Finally going to therapy. What should i expect or be cautious of?

I have two appointments with 2 different therapists, the first one im going to i sort got pressured to book or rather I couldn't really say no and the second one is a therapist I sort of connected with and im looking forward to seeing

I guess what should I expect? I know its pretty broad question but I'm just on the edge because I'm scared to open up and talk about things I've never told anyone before, im scared to be vulnerable to a person who might not be the right fit then I would just feel way worse about opening up. Idk im overthinking it but what do you guys think