There are a couple of small things that are, relative to the other components of the interview, much less important than nailing the behavioral and technical portions of the interview. Still, they can make a difference - especially beyond the interview.
At some point of the interview, you'll often have a chance to ask questions to the interviewer about the firm or the job. Most people I've interviewed dramatically underutilize this time.
One common mistake I see candidate's make is asking questions to show off how much they know. This is usually a well-intentioned attempt to signal interest. However, you probably you don't know that much about the job. A more positive variant of this, however, is when candidates ask about a problem I'm working on and - as I tell them - ask questions about whether it would help to try X. While it's rare, I do have candidates give me new ideas that I can try. In the best case scenario, I'm impressed. In the worst case scenario, I'm still grateful that they showed real interest in my work. In all cases, I leave feeling like they were interested in the type of work we do. These candidates succeeded because they got me to talk about myself / my work and they listened - then they found the right questions.
The more common mistake is that, when trying to learn about the firm, people ask lame questions like, "What do you like most about the job?" To be clear, I'm happy to answer that question and I don't think an interviewee is bad or uninterested because they asked that. However, I don't think my answer is helping them much. Will my answer to that really tell you how much you'll want to stay on the job? Will it really tell you if the company is better or worse than it's competitors, who you could also work for? Be as pointed as you can without being rude. Here are some suggestions:
When you think of people who have left [Company X], what are the most common reasons for leaving?
What is your least favorite aspect of X? Do you think it's a feature of the industry (e.g. sudden, rush deadlines in consulting) or are your competitors different (e.g. software as a service at Amazon vs. Google)?
What are the unique benefits of working at X? For example, it's well known that Google and Facebook pay more than Amazon. It's also well known that Amazon gives its employees much more autonomy - and generally more interesting projects - than most other tech companies.
Do you see yourself working here in five years - and why or why not?
Write thank you notes. I've never heard of this changing an interviewer's mind about a candidate's interview with them, but it does change how they perceive the interviewee. This will only help you if you actually accept the job offer, if you want to interview with the firm again in the future, or if the interviewer changes jobs in the future and you want to work at their new firm! Your thank you can be short and sweet. When I'm interviewed for a job, I look up the person on LinkedIn and send them a 250 character thank you note, mentioning one specific detail of our interview so they know I paid attention to them. As I mention in "behavior interviews", specificity makes communication more compelling.
[For the AEA / ASSA interviews] Wear shoes you can run in. I had to run everywhere all day through a foot of snow in Boston. For me, standard dress shoes can work fine, even in snow or ice. If you're not sure about your shoes, it would be worth testing out the shoe before the conference; look for something that allows you to at least jog at 75% of your max sprint speed and performs decently on slippery surfaces. Getting to an interview on time looks better, and just as importantly, an extra five minutes for the interviewer to ask you questions can be a huge difference in whether you make it to the next round of interviews. If we don't have time to cover certain material with you, even due to circumstances beyond your control, the risk of bringing you for a (costly) interview on site goes up.
[For the AEA / ASSA interviews] Bring enough snack bars and sports drink with you to feed yourself for the entire day. Plan on not having time to sit down between an early breakfast and a late dinner, so you'll need to refuel on the run. The snack bars were helpful but, after having interview days with and without it, I swear by the Gatorade. Intellectual activity depletes blood sugar and your interview performance will go up if you can quickly replace lost energy.