MMA gyms tend to fall into two distinctly different camps. The first will try to push all women towards their 'fitness' classes and away from the application-based fighting sessions. The other type will force everyone, male or female, to jump into the training program geared towards experienced fighters in order to create more punching bags for their pro's. This binary system, of course, has some grey area, but it is important to be aware of these two primary thrusts. In one they want to limit you because you are a woman, in the other they don't give a shit who you are as long as they can practice kicking the shit out of you.
Enough with the hyperbole...let's talk about how to choose a gym. MMA is a growing sport; there are schools cropping up all over the country (and the world) and some traditional martial arts gym are now claiming to teach MMA. But what makes a good MMA gym for someone looking to get into the sport?
A good MMA gym for newbs will teach basic boxing, kickboxing, wrestling and submission wrestling technique. One of the MMA gyms where I used to train offered no technique, so anyone new just had to watch and emulate the other fighters. The result was a whole lot of ugly, even from the so-called seasoned fighters at the gym. Every once in a while I took pity on some poor bastard and showed them how to do a hook, but I was one of the few who did.
I am all for ugly, underground gyms...I own one. But there is a world of difference between a simple, slightly dirty gym and a cesspool. Ringworm may be a standard fixture in the life of any wrestler or MMA fighter, but there are other, more dangerous bacteria to be reckoned with. Staph can be devastating, even deadly, and mats that are not cleaned regularly can easily transport the infection to an exposed back or leg. So how do you tell (beside the freaking obvious) if a gym is too unsanitary for you? When you visit a gym, check out their bathroom. Mama was right; people can tell a lot about your habits by visiting the bathroom.
So many people choose gyms based on the fight record of the primary instructor. This can be a mistake however, seeing as those big-named instructors may never appear at any training session. Also, the greatest fighters do not necessarily make the best teachers (i.e. Freddie Roach). Instead, choose a gym that has an instructor that you can talk to and who seems genuinely interested in your well-being. Although as a beginner you may be working with more experienced students than the primary instructor, it is still important that the head-boss is concerned with the health and happiness of his or her clients. One of the best ways to learn about an instructor is to talk to the other students. A person can tell you how awesome they are all day long, but doesn't it seem more legitimate when someone else confirms it? A good instructor will have students who are ready to rave about them.
A lot of women start training combat sports under the assumption (or desire) that they will never have to work with men. They will choose gyms that have all female classes and stay away from the "guys class" which in most gyms is not restricted to men but devoid of women. If this is what you need to feel comfortable, go for it. However, I think there comes a point where in order to grow, you need to move beyond your comfort zone and train with the best fighters in your gym, be they male or female.
Another concern is sparring, which depending on the school where you train can be compulsory or non-existent. I think that everyone should spar, but look for a place where they introduce you to sparring rather than just throw you in. Again, all this is based on the overall instruction and how they see their clients: as potential fighters/fodder or as individuals.