I only looked at schools in the U.S. and then looked at about 20 I would go to if I got in. Out of those, I looked at the ones that I realistically had a chance of getting into. I looked at each school's website and calculated the percentage of OOS female students that were accepted (since I am not competing against males). Then I decided on about 10-12 schools. I recommend applying to about 10 schools that you would go to if you got in. That way you have options. I have friends who only applied to 4 or 5 schools with average stats, and they barely got into one school.
I also looked at which schools let you switch to IS tuition after the first year. Those schools are Davis, Ohio, Missouri, and Washington.
I looked at the prerequisites for those schools and saw what i had done, and what I needed to still complete for the school. I cut out any schools that required classes that I did not want to take.
I then looked at how much work it was to apply to each school (how many essays on vmcas and how many essays for each supplemental). I factored that into how much time I had in the summer to devote to my application, PS, and essays. I chose the ones that I wanted to take the time to write for.
Hope this helps!
Most (all?) vet schools consider male and female applicants to be in the same pool, so I'm not quite sure what you mean by that. Could you elaborate?
Also, I honestly think that applying to 10+ schools is expensive and excessive. I could barely afford to apply to 4 when all was said and done (VMCAS, supplementals, interview costs). Keep in mind, too, that applying to that many schools means that you will almost inevitably have scheduling conflicts with interviews, so you will likely have to turn at least a couple of interviews down. That's a lot of essentially wasted money... I mean, do it if you want and can actually afford it (it is your money), but in general, I don't think that's great advice.
Anyway, in order of importance, these are the factors I considered when applying:
1. Cost. I know we beat this horse often on SDN, but seriously... unless you happen to have one of the more expensive schools in your state (e.g. UPenn, Tufts, MWU, UMN), apply to and do whatever you need to do to get into your IS. Not only is it almost always going to be the cheapest option, but also likely your greatest chance of being accepted. If you're in a state with an expensive school or you're OOS everywhere, seriously consider moving and gaining residency in a state with a cheaper option. I know of a few classmates who basically applied to ISU as OOS on their first application cycles, got in, but then declined their acceptances to move and gain residency in Iowa in order to qualify for IS tuition on the next cycle. Every one of them is thrilled with that life choice. There are a few schools that will allow you to switch residency status partway through and there are also multiple schools that will give veterans (and sometimes even family members of veterans) IS status. Just... seriously try to do whatever you reasonably can to get IS tuition. You'll still be in debt, but you will thank yourself later. Consider this ESPECIALLY if you have undergrad debt.
2. Pre-reqs. I still do think that applicants should do whatever possible to have a fighting chance at their IS, even if that means taking classes online through another school because your undergrad institution does not offer it (my undergrad did not have an animal science or animal nutrition class, for example, let alone an animal science department), because the cost difference between IS and OOS tuition at most vet schools is still far greater than the amount you'd spend on taking that class. But I did also apply to a couple of OOS schools. That being said, I had pre-vet classmates in undergrad who applied to OOS vet schools not knowing what the pre-reqs needed were and were thus confused when they were auto-rejected from, say, OkSU without having had animal nutrition. Really do your research here before applying so that you can spend your money in the smartest way possible.
3. How well the application jives with the admissions criteria. Look at the previously accepted classes' stats at the schools you're interested in and evaluate how well your numbers stack up to the averages. There are some schools, like Wisconsin, that I ruled out based on this due to a low cumulative GPA. On the flip side, I applied to ISU and a couple of other vet schools like it largely because their academic evaluations strictly only considered science and last 45 hours GPAs, both of which were far higher than my cumulative. Which GPAs are most important to the schools you're interested in? Is GRE weighted heavily and, if so, where do their average scores generally fall? Does the school seem to value variety in experiences, or depth in the area you're most interested in? These are things you really should try to investigate and at least consider when applying.