Apart from interviewing employees what other method can one use to determine that someone is capable that particular job?

Assess:

1. Knowledge.

2. Skills.

3. Attitude.

Besides a simple interview, I suppose a short, relevant close ended set of questions in the form of an aptitude test works well. But the one thing that works almost all the times is an immediate test of his/her abilities right at that moment. For eg. If it's a sales related job, the candidate can be handed over a simple object around and asked to make a sales pitch for it. The thing that this procedure tests best is the candidate's ability to think on his/her feet.

Hope you find this helpful!