Since this is a recurrent issue in my seminars (but also applies to theses), I want to give some guidance about what I consider a good paper (although other people might see things differently).
You might think, writing well is a negligible extra skill that you should not spend much time with, as it distracts you from becoming a good economist. In fact, it's not. Not only will writing well help you clear up your economic mind, it will also be a key skill once you become a professional economist, as a key part of your work portfolio will be writing memos, briefings, and reports.
The following thoughts and ideas might thus be helpful, not only for delivering a (very) good term paper, but also for your future career progression:
1. Writing is thinking
There is a strong connection between our language and the way we think. As Paul Romer once said: "“Clear writing really is all about clarifying how we think about things.” That has some implications.
First, like thinking, writing needs time. A lot of time. This is especially so because our writing tells us which aspects of a topic we do not fully understand yet. It might have seemed clear in our head, but now that we want to write it down, we get stuck and do not get it on the paper in a meaningful way. Although some of us find it more difficult to write down stuff than others, this often is a sign that we did not get the essence of the topic right yet.
Thus, plan ahead accordingly! Don't think of a semester seminar as getting as much into your head for most of the time that you then "simply write up" in the last two weeks before the deadline. Start writing early! In the best case, you will have a rough draft/outline of your paper already before your seminar presentation. This helps you identify your weak spots and questions for the seminar. You should then considerably revise your paper about 1-4 weeks after the seminar (if the exams allow for it). This might significantly change the structure, arguments, and story of your paper, taking into account the feedback you got at the seminar. Presentations of your fellow students might also help you contextualize your paper. In the last revision (2-3 weeks before the deadline), you just fill in some new information you might have learned and do the tedious legwork (polishing sentences etc.).
Yes, I know, this is a lot of work. I know, because economists are not scientists who just "write up" research. As John Cochrane rightly says: "We are primarily writers. ... Most good economists spend at least 50% of the time they put into any project on writing." So even if you are a good writer, plan to spend at least half of your semester seminar work on writing. If you are not, accordingly more.
Second, I can only judge (and grade) your paper on what is written in there. Even if I might think you are a smart student and get the idea right, when focusing on the paper I will have to assume that if it is not well written, it is probably not carefully enough thought through.
2. Tell a story (over and over again)
Do not see your paper as a collection of facts. Even though your paper has way higher scientific standards than an essay, treat it like one. A good essay has a clear main argument and according storyline, together with a sound flow of words and sub-arguments that support the main argument.
Having (and exploring) a hypothesis is a natural way that helps you follow a storyline. Another practical advise is to write down the essence of your storyline in 3-5 sentences (and to put a lot of thought in that). Then ask yourself at each paragraph, argument, and sentence: How does it fit into the storyline? Oh, and if you need more than 3-5 sentences for your essential storyline, its probably not a good storyline. In the most radical way, you can think of your paper (sub-)title as the key storyline. "Growth is good for the poor" -- *bam*, there you go.
3. Your paper is not a novel
Be aware that an essay is something else than a novel! The punchline of a novel often rolls out at the very end. The punchline of your paper should be upfront. It should come out at least three times in the paper: once in the introduction, once in the main body of the paper, and once in the conclusion. Better make if five times if you are not a very good writer and/or think your audience is not paying as much attention to your thoughts as they deserve. As you are dealing with economists, really...better make it five.
What applies to your paper, by the way, also applies to your seminar presentation: do not build a complex story that you will then conclude at the end, expecting the audience to be thrilled about your amazing conclusion. In the most likely case, by the end we are either confused or asleep.
4. Beef up your arguments
Once you set up your key storyline, you will set up a chain of smaller arguments supporting this storyline. Especially the essential arguments you need for your storyline should be supported, either by reference to previous work, graphs, or a model.
5. Review the literature under the viewpoint of your storyline
Accordingly, when doing a literature review, do not simply list what authors A, B, C have done. Explain their contribution and findings in light of the story you want to tell. This does not mean that you should only discuss literature that supports your storyline. On the contrary, you should reflect on all the work that relates to your topic, but focus on those aspects that are really relevant to your question. And if some contribution's findings go against your storyline, tell upfront why you think the author is wrong or why her findings are not of relevance to you. Maybe she looked at another time period? Or she has no clue what she is doing because, obviously, X in her equation uvw is endogenous...
6. Think in topic sentences
When I was working for the World Bank, I had to start writing reports with topic sentences. Basically, this means putting the first sentence of every paragraph in bold, which should highlight the content of the paragraph.
I understood that this helps the reader to quickly skim a long report (World Bank reports are extremely long and readers usually have better things to do than reading the whole piece). What I did not know beforehand is how much writing with topic sentences changes (and improves) your writing (and thinking!). By checking your topic sentences, you are structuring the flow of your arguments, and can always check whether the storyline rolls out smoothly. Plus, you can simply put a topic sentence where you have a good thought, and fill the precise content of the paragraph at a later stage.
My suggestion is thus to write your paper with topic sentences. Before submitting, delete the topic sentences (either delete them, or change them from bold into regular text if the topic sentence is genuine part of the paragraph).
Yes, this might seem a bit tedious and odd. But I tell you why it makes sense: If you are seriously struggling with your writing skills, this method is extremely powerful (so benefits outweigh costs). If you are a good economic writer, the chances are that you are doing this anyway in your mind, maybe without noticing (so costs are almost zero). Finally, if you think you are a good economic writer and find out this is not what you are doing, you have something to think about... (benefits will outweigh costs!).
7. Be clear, how causality runs
This relates to 1. ("Writing is thinking") and might explain why economists are obsessed with causality (the other option being that our pseudo-mathematically-wired minds are just able to digest sentences like "from A follows B", A --> B). Accordingly, make sure your chain of arguments represents a logically consistent causality (or is it just a correlation?).
Once you really understand what is going on in an economy (or in a model thereof), it should be way easier to walk your reader/audience through your chain of arguments. On the other hand, if you establish a causality in your paper where no causality exists, this indicates that you have not thought through the subject. Its not only an indication that you mixed up things a bit, its an indication that you missed the essential point of the whole thing! So be cautious on establishing causalities; and in cases where causality might be dubious or not straight-forward, beef up your argument why causality is running this way (see 4. above).
8. Write in short, clear sentences
Especially native German-speakers tend to form long sentences. Probably that has to do with the structure of German language and with German history (see also 9. below). Some of us are gifted with the ability to form long, elegant sentences that are still clear. Most of us are not. So try to keep things simple.
Avoid words or phrases that introduce mind-acrobatics ("Although...", "Despite the fact..."). This "pros-and-cons" thinking is very strong in German philosophy, I know. But modern economics reasoning follows more Anglo-Saxon principles. Thus ask yourself: is the "con" essential to your "pro"? If not, leave it. If it is, it deserves it's own sentence, paragraph, or section.
Finally, chances are that long sentences become vague and imprecise. However, I have to judge and grade your paper on the clearness of the economic argument. So strive for clearness in your language and follow Antoine de Saint Exupéry: "perfection is attained not when there is nothing more to add, but when there is nothing more to remove."
9. Use the active!
The passive is very sparely being used by good writers. Good writers use the active. This cannot be stressed enough! :-)
Using the active is strongly connected to our way of thinking (point 1.), as good economics writers do not simply turn passive sentences into active ones. They think (and accordingly, write) in active voice, not at least because they are aware of the importance of causality (point 7.). Active tense helps establishing causality and effects. Accordingly, if you are not sure what is going on, you are more likely to fall into passive voice (as you are just observing/describing an effect without having anything to say about the cause). Active voice will thus also help clearing up and shortening your sentences (point 8.). Writing is thinking!
A note on formatting
I am not particularly picky concerning formatting guidelines (which does not mean you should not care about a nice layout of your paper!). However, you make reading your paper easier to me if you use footnotes instead of endnotes and put your graphs, tables etc. in the main body and not to the end/appendix of the paper.
Further resources:
I hope the above thoughts help you to improve your term paper and become a better economist. At least they should help you understand what I consider important in a (term) paper, however, they are no complete guidebook how to write well -- especially as I am not considering myself a particularly good writer. I just enjoy writing, which makes it a bit easier to put effort into it (would I have written this otherwise?). Other people have way more knowledge on the subject, some of them the most outstanding economists. If they care about good economic writing, probably so should you:
Greg Mankiw's How to Write Well is a concise and helpful checklist, which is also fun to read.
John Cochrane's Writing Tips for PhD Students also apply for Master students, although your seminar papers will usually be shorter.
Plamen Nikolov summarizes various tips for writing economics research papers.
Keith Head gives advice on how to write an Introduction, Marc Bellemare knows about the Conclusion and anything in between.
Deirdre McCloskey has written a lot about economical writing. Here is a very brief summary of her book, which is also available as a (somewhat shorter) paper version.
If you take writing serious (and you should), The Elements of Style should be your most helpful companion.
John Ken Galbraith's article explains how important writing is for economists, and how much work and attention it deserves; with a great sense of sarcasm.
Whitman College's Concise Guide to Writing Economics Term Papers -- focuses on the standards at Whitman's, but has some important thoughts in the first three sections.
The Economist Style Guide provides an elegant (and funny) overview and various specific guidelines.
World Bank course: Report Writing -- this online course is certainly influenced by the World Bank's corporate perspective and needs, but still includes a lot of helpful thoughts.
Chris Cunningham has a Twitter threat laying out guidelines for writing good policy briefs for undergraduates.