Typing speed & problem solving skills (specifically, is their first instinct to ask a peer for the answer/help, or research/independently figure it out). The rest of it is practice. If your project requires more algorithmic stuff, then check for math background. If it is IT stuff, I have found people who win programming competitions do really well (the ACM programming competitions during my school days taught me - take a barely sufficient approach, focus on the problem and only the problem, speed of execution, .. something that helped me in my career).
I lost count on the number of people I have interviewed that said they were a top developer, yet, were one-finger typers. But I am old-school. The kids nowadays are just amazing.
