I always ask technical questions about the subjects the candidate claims to know, the areas of knowledge highlighted on the resume. I want to see how comfortable they are talking “techie”, how well they can explain something. If they don’t have the goods, they don’t get hired.
I have made mistakes in hiring enthusiastic, go-getters who were able to con me into dropping my concern about their shaky technical skills. A few months later everyone is sick of the used-car salesman on the team who never gives you a straight answer, who is continually overpromising and underdelivering, who skates away from responsibility, and whose winning personality translates into a losing team. Give me the brooding backroom tech guru everytime. I can figure out how to harness their talent and make them effective contributors. But you can’t do much if they don’t have much to contribute.