Seeing a Therapist

I'm going to see a therapist who specializes in LGBT related issues for the first time in a few days. I have a psychiatrist that I've told about me, but she couldn't really offer much advice because this falls outside her area of expertise. I'm pretty open about myself to all my family and friends, but I'm really starting to feel like I've hit a wall lately. I just feel very nervous about talking about it for some reason. So I'd like to ask everyone: What have been your experiences with therapy?

How did you approach the subject?
Did you go in with a particular goal in mind?
Did you have trouble opening up? If so, how did you get past this?
Overall, how helpful was your therapist?
Did you feel the need to go dressed up, to legitimize your feelings?