"hire slowly, fire fast"

sounds like good advice to me. I'm surprised how hard most people seem to find firing people. I mean it's usually pretty clear within the first month or so if you made a mistake, and at that point it's not like they have a lot of company-specific knowledge, so I think at that point, often it's best to apologize to the (now ex) employee for the hiring mistake and part ways.

Hiring good people is hard, and you are bound to make mistakes. It seems to me like you need to have a procedure for correcting same.

"human qualities"

You need to be careful here... turning away a good programmer because she has a touch of auspergers usually means you end up with a mediocre programmer. If programming is core to your startup, hire the best programmers you can get, and then hire other people who are compatible with the programmers personalities.

Of course, if your startup is largely marketing focused, a mediocre programmer who can deal with your marketing guy might be a better choice. But my point is that you don't need everyone on the team to be socially skilled or friendly- but you do need to make sure you have compatible personalities.