I'd be one of those who says SubI aways tend to hurt more candidates than are helped. But, to answer your question, here it is:
1 - Your mission is to make your team look good, so:
a - do know every lab, every radiograph report, every path report on every patient as soon as humanly possible. Don't jump the line, tell the most junior resident first if possible (interns from other services not included).
b - do round on every patient on the service and write notes if allowed even if the team says it's not necessary. It may not be, but doing it and doing it well will set you apart
c - don't answer out of turn. If a resident is getting grilled and they don't know the answer but you do, don't shout it out. Wait until you get asked. Looking like a know-it-all might help you in the eyes of the attendings but if you piss off a resident you're going to really make it hard on yourself.
d - do be the first to scrub out of the case to do scut, don't stick around just to suture something if that makes the junior resident scrub out to round
e - don't be obnoxious. don't tell about all your great accomplishments unless asked. don't brag. Your hard work will win you questions that will then set you apart
f - never talk another student, resident, attending down. ever. Even if others are jumping on someone you can laugh along if appropriate but don't bite and add your own 2 cents.
2 - You need to look good, so:
a - be underfoot. I want my subI to be grabbing a CT or pulling it up on PACS when I show up to do it. Have bandage scissors ready when I want them. Same with a stethoscope. Yes we still use them.
b - dress appropriately. Always wear a tie. Always change out of scrubs into professional clothes if possible even if the residents don't. Your job is to look good as much as possible, not comfortable.
c - don't ask questions to make yourself look smart, that is so transparent. Ask real questions when you have them. The more intelligent the question, the better you will look. In general, if it's easy to find in a book, you probably shouldn't ask it. One exception can be in the OR.
d - KNOW your anatomy backwards and forwards. It's the most common thing you'll get pimped on. You have to know this because the good students will. Read every day, every night. Read the basics first. ENT secrets, KJ Lee, not Cummings.
e - KNOW the case before you arrive in the OR. I mean know the indications, the anatomy, the patient, the pathology, the radiology. KNOW IT!!!! The actual procedure itself isn't as crucial, but knowing why it's being done, the potential complications, and the pathophysiology of the presenting issue are absolutely crucial.
f - spend time with the chairman when you can. No one has more power to make or break you. This is a delicate balance. Too much and you're a pain in the butt, too little and he/she won't know you.
THESE ARE THE 2 POINTS I CANNOT POSSIBLY EMPHASIZE ENOUGH:
If your team loves you, your golden. You make them look good, they'll love you. They love you everyone hears how great you are. Everyone hears how great you are, you've done your job. You will have a significantly higher chance of a high ranking in the match when you've done your job.
Never, ever get outworked by anyone and never look miserable. Smile like Phil Mickelson choking away the US Open. No one should outwork you. Period. Not the attending, the chief, the R2, the intern, the other SubI(s). NO ONE!!!!
. How do programs feel about students who do multiple aways, especially in the same city? 
