That said, here are a couple of ideas that come to mind to get a better feel for a company. The nice thing about both of these is they benefit both the employer and prospective employee.
1) The best way I know of is if you're referred to a company by someone you know and can trust enough to tell you about the warts beforehand.
2) Failing #1, if you find a company you're interested in and who's interested in you, ask them for a contract-to-hire position with a 3-6 month or so contract. It's a great way to really get to know the culture without a huge commitment. They'll do it if they want you, but if they balk you should be able to convince them it's in their best interest as well. Just don't do anything drastic like relocating until you're fulltime.
Anyway, good luck.