I agree with what Mel said. Knowing how to present concisely yet effectively is half the battle. And having a solid ddx for the top 10 things or so you are going to see is great. Those two things will make you look stellar.
Otherwise, I had posted this before in another thread, but dug it back up and will copy it here. It's my best advice as to the "little things" that will help you standout.
1. Show up 10 min early to every shift. If you are late, even once, and someone writes about that on your SLOE (I see this several times a year reading applications), it looks AWEFUL!
2. Don't be hard to schedule. If the chief residents make the students schedule, and you have a ton of requests and are a headache, I guarantee you that chief resident will tell EVERYONE about it
3. At the beginning of the shift, find out who you are working with. Are you assigned to a resident or attending. Introduce yourself, and ask them how they'd like you to approach the shift. Some might want you picking up charts anytime. Others may prefer to hand you charts. Everyone has a different workflow.
4. If you work with a resident, do anything you can to help them. I can't stress this enough. Residents probably have more say in boosting people up, and dropping people down, the rank list than some attendings. PD's don't want drama. They don't want to deal with residents who don't get along. And residency is tough. So if you can do little things that help the residents, I promise you, they will lobby for you.
5. Don't ever lie. If someone asks you a question like "does the patient have any vomiting" and you didn't ask, say you didn't ask. Don't say "no" and hope you are right. Because if you get caught in one lie, noone will forget it.
6. Be courteous and nice to the nurses and ancillary staff at all times.
7. There is too much focus for students on seeing more patients. Its great if you can see 10-12 patients a shift, but if all you are doing is an H+P and never following up on anything, never rechecking anyone, and never updating the person you are working with, then you are basically creating more work.
8. Understand that sometimes, you may get pushed aside. The ED can be busy and chaotic. Sometimes, an attending/resident may just not have time for you to pick up another case with them. They are often carrying a huge patient load. Don't be offended or take it personal. Offer to help out in anyway you can.
9. Read and follow up on your cases. If you see something interesting, it would be crazy impressive to see the attending a week later and tell them "remember that patient with delirium the other night? I looked him up, and it turns out they found..."
10. Don't just followup labs/xrays. Anyone can do that. Students shine when they followup on the patient's themselves. I promise you, if you go back and see a patient and catch something that wasn't caught before (patients do change over time), they will be VERY impressed
11. Lastly, time yourself in the room. Strive to eventually be able to get out of the room in 10 min or less. Thats not going to be feasible when you start, but it eventually needs to happen. You'll learn what is essential to ask and what isn't. You're job isn't to do a medicine H+P. It's to do an ED note. Focus on high yield questions about the chief complaint, don't get tied down in the ROS and not flesh out why the patient is actually here. There will be patient's that make this hard to do, but getting out of the room faster is essential for you to impress residents and staff.