Pick out someone, ask their advice on an exercise. say hello every time you see them and perhaps ask for further advice. after a week or two you should have a pretty good idea if they are someone you might want to train with and then just ask them if they would take you on as a training partner.
that is exactly how I landed the BEST training partner I have ever had. He shows up every time without fail, pushes and spots me like a champ, and two years later, he is one of my best and closest friends. I have also charted my progress since I began training and a good partner makes a huge difference in both strength and size gains.
I came out to him about 2-3 months after we had been training because I could no longer hide my "old lady" from him without damaging our relationship. When I told him he was stunned and a little scared. He had a pretty rough time with it for quite a while. From that point forward I have been completely open and honest with him and it's been great.