Oh, what the heck. I'll take a stab at it.
1) Just concentrate on being the best 3rd year you can be. Get everything you can out of every rotation, and don't be so obsessed with the ultimate goal that you miss out on the little details. The ultimate goal may well change, and you shouldn't blow off the minutiae of of some specialty you thought you didn't care about, only to find later that you're into it.
1a) If you don't love the ER, you won't be able to talk yourself into loving it. Don't go into EM for any reason except that you enjoy the work. "Burnout" is just a shorter word for "I wish I had done something else."
2) If you can do your EM rotation after you've had some Cards, OB, or Neuro, you'll have some handy factoids and diagnostic stuff under your belt that are almost certain to be helpful in the ER. Plus, depending on the ER, students are usually allowed considerable latitude in assessing the problem and devising the plan. If you are at least somewhat good at this, the rotation will be way more fun.
2a) Emergency people have plenty of time to teach (in fact, many of them love it, and I've seen attendings "show off" something cool or interesting for students), but they do not have time for BS. Wrong answers and honest attempts are fine; lazy thinking and half-assed work are not.
3) Doing a rotation at a site where you want to match is cool and all, but a really strong letter from ANY department with an EM residency is the best thing you can get.
4) The best skill you can have as an EM provider is to know what resources you have available, and how to use them. For instance, the search function and the stickies should serve you well here.
5) This is the part where the thread degenerates because it's a well-worn question, and there is almost as much to learn from the goofy answers as the boring ones. There have been several really good "how-to" and "so you wanna be in EM" threads.
5a) If you have specific questions, ask them. "Any tips/advice" can easily be mistaken for "spell it all out for me," which is so much less helpful than you figuring it out your own way.
