Conversation, half technical and half to figure out what the person would be like to work with. For example, tell me about the most interesting/difficult/satisfying problem was that you've worked on. Or, tell me what happens when you point your browser at a web site, in as much detail as you can muster. What are your go-to tools to solve problems
Mostly pair-programming coding session on site or homework that is later discussed and "developed" on site. Candidate picks which option works best for her.