1) Create a new email
This cannot be stressed enough because it will make your life so much easier and more organized.
a. You don't want to use your school email for college applications because anything you have connected to it will be deleted after you graduate, and it may be important information to save, especially if you are accepted by a school
b. Your personal email will get bombarded with college emails, and it's much easier to keep them all in one place and everything together if you just create a new email account solely for college applications and scholarships. Additionally, if you don't make a new email, you may be overwhelmed by the sheer number of emails you're getting and may either miss something important or accidentally delete information for a college portal/other important info regarding your application.
c. When creating a new email, make sure it's your name or something professional. Colleges can see your email and will judge your character based on it, so kittenlover123@gmail.com, it's time to change that! (You may also want to consider changing your profile picture too if it's really strange.)
2) Social Media Presence
Colleges can look at your social media/if you say or do something inappropriate (etc.) on social media, people can and will send it to your colleges, and you may be rejected or your offer may be rescinded based on how you have presented yourself.
An app that allows you to connect with other students applying/prepping to apply to the same schools as you. You can ask questions, find roommates, and find people at a college with similar interests to you.
A subreddit that describes itself as "the premier forum for college admissions questions, advice, and discussions, from college essays and scholarships to SAT/ACT test prep, career guidance, and more."
It is chock full of good information pertaining to the entire college admissions and decisions process, and more than likely if you have a specific question it has already been answered on there (or you can make an account and post the question yourself).
5) Try to get your applications done a few days before the deadline
Coming from someone who stayed home on New Year's Eve watching Fight Club and finishing college apps, instead of going out with my friends, you DON'T want to wait until the last minute. Your essays will come across as rushed if you do and might not truly present you and your feelings about the school. Giving yourself a few days before the deadline does a few things: 1) creates a lot less stress on you 2) gives you time to edit your essays and possibly have other people edit them 3) prevents any last-minute issues that may come along with you and just about every other applicant submitting your application at 11:57 pm on the night of the deadline.
The Common App typically refreshes every year on August 1, so I would personally avoid filling it out until then. There are typically slight changes in it each year, and you don't want to have to fill it out all over again if something happens when your information rolls over. The Common App also releases its essay prompts on August 1 as well, and they typically vary slightly from year to year. However, even if you write an essay that doesn't directly adhere to their prompts, there is normally a prompt to submit an essay on any topic of your choice (as long as it's appropriate!)
7) Avoid admissions calculators
Now, you may be asking yourself why? Why would I want to avoid seeing how likely I am to get into a specific school? Well, many schools' admissions are holistic, meaning that you are not accepted based on a singular portion like your test score, it is a combination of all the parts of your application together. Admissions calculators usually only take into account your test scores and GPA, rather than your letters of rec and your essays, and don't give an accurate representation of the likelihood of you getting into a school. For example, based on my GPA and SAT score, an admission calculator suggested that I had an 84.27% chance of getting into Boston University, which means I had a strong chance of getting in. However, I got rejected. This is because these calculators cannot take into account outside circumstances (ex. an increased number of applications, and fewer spots; different acceptance rates for different majors), essays, letters of recommendation, and how well the admissions office believes you would fit into a school. Moreover, they just cause a bunch of unnecessary stress and anxiety and can make you feel like your worth is equated to how well you are able to answer a bunch of multiple-choice questions.