If you like listening more than talking then you're halfway there.

Showing warmth and that you're not a dick means listening to other people and responding to what they say (In my opinion). That may be an oversimplification.

I went for lunch with my sister a few months ago, she was having trouble making friends and being warm and open to new people. When the waitress came over I chatted with her a little bit and joked around because she nearly tripped as she approached our table. When the waitress left my sister asked me if I knew her - I didn't. She thought I had because of how we were talking to each other. I gave her a tip that she said completely changed how she approaches new people - she was already trying to just listen to what other people say and asking questions when it was her turn to talk but the thing that made it click for her was that I suggested to her that she should try pretending that they're already her friend. That tip made talking to new people easier for her. If you talk to people like they're already your friend then it's easier to be yourself, genuine, and warm and be interested in who they are.

It might work for you - your milage may vary.