Depends on the topic of conversation. Depends on which friends it is--that is to say, you and her, 'her' here obviously being a girl, which makes all the difference, adds an air of tension that is sexual in nature--depends on what you do during that drink.

She'll put her hand on the table, you'll reach over to emphasise your point, and just touch your fingertips to her hand--and, bang, that's where it starts. Simple.