Hi there everyone!
So you've decided you want to sign up for the match. Congratulations (sort of)! Next comes the part where you sift through the hundreds (yes) of potential internships and decide which ones might be for you. Here are some hints to help you with that:
1. Sit down with yourself and figure out why you're doing an internship.
If you are doing an internship as a prerequisite for a residency, know that academic internships and fancy/famous private practice internships (read: the AMC, Angell Memorial, etc.) are rumored to better your chances for matching to a residency.
This is because these institutions are well-established, (usually) well-respected, and oftentimes have residencies in various specialties as well. Some institutions take their own rotating interns back as residents (hey, the devil you know...), and some prefer not to do that.
The tradeoff is that your hours will be unbelievably, potently terrible, and you will (probably) spend a large amount of time watching other people do cool things instead of doing them yourself. It will be so crowded at the operating table.
If your goal is to learn how to be a veterinarian in a practical sense so you can be a solid general practitioner or ER doctor, I would strongly consider a solid private practice internship. You will (usually) see more cases, get more hands-on experience, and get to do more cool things yourself.
I did my rotating internship at a well-established (but not fancy/famous) private practice internship. As such, I spent absurd amounts of time working in the emergency room, saw many many many cases, and got to unblock more cats, enucleate more eyes, do more bone marrow aspirates, drive the bus during more endoscopies, practice more ultrasounds, repair more wounds, figure out more weirdass 4 am puzzles, and help with more dog and cat CPRs than the average academic intern.
At an academic hospital, the chiefs of service are doing their research, seeing some cases, and lecturing. They are also training the residents, the vet students, +/- the specialty interns, and the rotating interns.
At a private practice, the chiefs of service are seeing their cases and teaching...you. You're (usually) not jockeying with a herd of residents, students, and other interns for various opportunities. It is awesome.
2. Next, figure out what factors matter to you.
Some people care about location. Do you want to be on the East Coast? Only in California? Only in places with appropriate attitudes re: the excellent variety of sexualities and gender presentations?
Do you care about having protected days off? What about vacation? Health care (Hint: you should care about these things, especially health care).
What about the percentage of time you'll spend working overnights? Will someone be with you on your overnights? If you're interested in neurology, it's probably important that you have access to a neurologist during your rotating internship.
You can use all of these and more to help you narrow your list of possible options. Be aware that there's no organization that oversees all of these internships and ensures that they treat/train their interns in a reasonable manner. Pretty much any place can register with the match and offer an "internship", which leads us to...
3. Once you have a preliminary list of practices - call, e-mail, visit.
Many places allow you to extern (spend a couple of weeks shadowing) to get a feel for the practice and how it works. If you can, arrange to do this at your top choices. It will be so very worth it.
If you can't extern or visit, make sure to call and speak with your potential boss/intern director and/or a current intern. DO NOT SKIP the "speaking with a current intern" part. Current interns are the most useful resource you have in your quest to determine if any given program is an earnest, enthusiastic training program for new grads, or a shithole salt mine that will tear away at the fabric of your sanity.
Ask the current interns if they like their job. Ask them what they like least about it, and if they would do it again. A favorite mentor of mine says it is easy to damn with faint praise, so be on the lookout for non-committal or evasive answers that are secretly your signal to run. The average intern will be tired, stressed, and out of patience, but if she can't say that the program is fair, forthright, and good training, don't rank it.
You guys, make sure you don't assume anything. Ask.
ALSO! Once more, so you realize how insanely important this is:
DO NOT RANK A PLACE IF YOU DO NOT WANT TO MATCH THERE!