Its a good thing you are starting early, it does take some time to set up. ( If you start late, you will just have less options because the away schools will be filled)
1- Look through websites of places you would like to rotate and what they want you to do.Call their medical education people to clarify. Each place has a different protocol. Some places will charge you an application fee up front while other only when you show up. Some places have a formal application process while others its just a phone call.
2- Look through the book at the OME to see if they already have a contract with UB. Most large places will. If they dont and you still want to go there, you can jump through some hoops and make it happen. If it a good program/hospital Dr. Nielsen will help you out. You need this contract because it UB pays for your liability insurance while you are away.
3- Apply for the away programs as soon as you can and wait till you are accepted.
4- For registration, register at UB for regular classes until your away elective is confirmed.
5- When you are accepted, many away schools will require you to get a doctors clearance with your immunizations on it. They request titers of the MMR or that you were given the MMR. ( I had a problem with this b/c my titers were slightly low and had to get another MMR vaccine. My advice is to get the vaccine from the get go b/c its a lot cheaper and neither are covered by the school insurance. Titer -$190 whole vaccine is around $30)
6- To register you need to get the away elective form ( I forgot the official name) from the OME website and give it to the department head of the elective you will be doing. They will sign it and fax it to the OME.
7- Each department has a course listed as " course at other university" thats what you want to register for.
Again, only register for away elective once its confirmed and register for UB classes otherwise. You will be doing a lot of drop add/forms after registration is closed but at least that way you are taking something you like at Buffalo instead of having to find an elective last minute.
As far as scheduling, some places will be flexible and will just give you the dates you want. Ask about it, I had one place where the website seemed really strict about not changing dates but when I asked the specific department they were fine with it.
If they away school is not flexible than UB will be. The only two classes that I took on schedule my fourth year were Neuro and Advanced Med. Basically, once you have the dates for your away rotations start contacting individual department or attendings that you will be working with if you know and see if they are OK with your change of dates or splitting up a module.
Most departments have something called Preceptorship Course. Basically, you find an attending at UB you want to work with and just work with them for a month. These people will usually be very flexible b/c it doesnt really make a difference to them which four weeks you show up for. ( For example, I did 3 weeks with a Ambulatory Primary Care MD - he went on vacation for a week and I made up a week at another dept and then when he returned I finished my last week.) Another flexible option is research.
The main thing to remember is that many departments will be surprisingly accommodating if you give them enough warning and have a legitimate reason ( like the away school wont let you chance the date). But do not expect to show up at the last minute and for them to change your schedule around. Like I said, lots of drop/ add forms.
Also, you can plan your vacation month before or after an away elective. That way your vacation is split up.
I know this seems overwhelming but its really not that bad especially if you want to live somewhere else. I only have about 4 months in buffalo during my fourth year and subleased my apartment the rest of the time.
Good luck and 4th year is going to be great =)