4th year is rough. Terrible. Awesome. Tiring. Boring. Uncomfortable. Interesting. Challenging. Humbling. Makes your feet hurt. Makes you dependent on caffeine.
It can be any or all of the above depending on the month.
If you pick a bad program, you could be bored to tears and hate the entire month. But you'll probably get plenty of sleep not stress too much.
If you stay with a buddy and end up sleeping on a couch, you will be uncomfortable. Weekends will be good though.
If you pick a really intense program, you'll get up seemingly in the middle of the night and fall asleep as soon as you get home. You may hate this, but you might like this too.
Some programs are more academic and you will constantly be asked questions. If you like the challenge, this may push you to learn and you'll get a lot out of it and show up the next day more prepared. If you don't, well you'll be miserable.
I guess the point is "it all depends". You have to first establish what you want in a residency. Do you REALLY want to get up @ 3 am everyday for rounds? Do you mind attendings with egos or a strict hierarchical structure? Would you rather just do surgery and some light clinic and then go for beers on weekends? Or do you have a family that you want to spend every night and weekend with?
So first, write down what YOU want in a residency program. This will probably include location considerations. If this is important to you, don't pretend its not. But schedule at least one month in a totally different geographic area so you get a different perspective and exposure than you are used to.
Next, start researching programs. Believe it or not, your school attendings are really the last people you should ask. Don't even bother. They will tell you to go where their personal friends work and normally they know very little about the actual programs.
The best people to ask are students who RECENTLY clerked at that program. Don't ask them "How did you like it?". That is far too subjective. Ask specific questions w/ concrete answers. "How confident are the 3rd years in the OR? Do 1st/2nd years DO any of the cases or are they just retracting? How many cases are double scrubbed and if so does the senior ever let the junior do anything or teach them how to do the case? Do the residents hang out outside of the hospital (if that matters to you)", etc
Asking current residents and recent grads of the program is also fairly useless. They just are not going to talk $*** about their program unless it was just god awful. You can ask them about their jobs or job offers (not $)
Another good research tool is just spending a day with the director, even as a 1st or 2nd year. If you can't stand them for a day, you know you wouldn't do it for 3 years. I can usually tell if I'm going to like someone within 15 minutes. This is a great way to cross programs off the list. I only did this once, but I know it saved me from wasting a month. Very politely email his/her secretary and rarely will you be denied.
Now you'll probably have quite a list of programs. I recommend adding @ least one very academic/intense program that will challenge you and force you to learn, whether you want this sort of program or not. Then schedule it FIRST. This will kick you in the butt and help you establish a good work ethic. So the next month you will 1) look awesome and on top of things, quoting journal articles, be prepared, and be oozing with confidence and 2) you'll hopefully keep reading and know what pace you should keep, so if you're on a lighter month, you'll still get a lot out of it. This will make you look better on subsequent months and help you prepare for interviews.
I would then go to my first pick the next month. Read up on the attendings and THEIR research and be able to quote that ###*, ESPECIALLY if they are doing a case in an area that they have published. You are studying for a test, and the right answer is whatever that attendings opinion on the subject happens to be.
Then schedule other programs as you see fit taking into account travel distance. I recommend adding something different such as a program that has a lot of wound care or other special feature that you've had no exposure to.
Ok, I'm too tired to keep going, but keep your eyes open when on rotations. You'll have to live it to see if you like it or not so don't believe everything you hear (especially from those far removed from residency training).