How do you escalate without making it weird?

Unless I'm with a very open girl how'd basically a happy extrovert. I don't really see how I can escalate touching. I'm out with a girl I think she likes me, but she's very reserved in her body language. She doesn't really pull away if I touch her arm or shoulder. But she doesn't ever lean in either in any way. So the method of escalating is something I need to improve.

How do you guys go about it?

Do you say anything? "let's go over her." and touch her hand? What's the game plan?

Yes stupid question but I feel so uncertain and I'm sure that shows with the girls. So I want to fix it