I always choose a random team. But I also rarely ever switch from that team I'm put on be it winning or losing. The problem is it usually takes at least two good players from one team to switch. One guy rarely changes the score in this game (most of the time). Unlike DM style games like say Counter-Strike where one guy can make all the difference in the world, in TF2 it can be one to three people just making that little bit of difference. There are exceptions like say that one Engy who somehow quickly gets his gun up every time you take it our or that one Demo who seems to always be right there with stickies or even that Pyro/Scout who is always on your ass keeping you in check. But most of the time you need that Medic and that Heavy that are never two feet from each other or that Spy that waits on your uber before he runs in and saps.