Our company is looking for new programmers. And here comes the problem - there are many developers who look really great at the interview, seem to know the technology you need and have a good job background, but after two moths of work, you find out that they are not able to work in a team, writing some code takes them very long time, and moreover, the result is not as good as it should be.

So, do you use any formalized tests (are there any?)? How do you recognize a good programmer - and a good person? Are there any simple 'good' questions that might reveal the future problems? ...or is it just about your 'feeling' about the person (ie., mainly your experience), and trying him out?

Edit: According to Manoj's answer, here is the question related to the coding task at the job interview.