Technical recruiting is a different kind of animal than regular recruiting. Here are some tips:

1) Learn how to use email. Since you are finding most of your candidates via email, it makes sense to continue communicating via email and answer question.

2) Technical candidates are not desperate for a job. These are usually smart people who have savings, and are looking for a career building job, not just a job.

3) Give a detailed description of the company you are hiring for. Keeping the company completely confidential is the quickest way to fail at technical recruiting. If you can't provide the name (which is best), be prepared to provide a detailed description of what the company does.