Before you even take a job, get clear on how often you'll be expected to work overtime and exactly how you're going to be compensated.
This reminds me of an interview I had back in '99 (right before the dot-com boom). As an EE, the interviews usually last all day, talking to about 8 or 9 people over the course of the day.
So who was the first person I talked to - the HR lady. Practically the first thing out of her mouth was "well here we pretty much work 6 days a week, and we expect people to do that". Well at that point I really didn't need to hear anything else she or anyone else there had to say. Mind you this was in San Jose in '99 when startups were forming everywhere and stock options were all the rage. In some places a 6 day work week was standard operating procedure.
Unfortunately for me, there is no amicable exit from those type interviews even when you know early on it's not going to work out. So I went the whole day, talked to everyone, and eventually even got an offer from them. For the cost of living there, their wage offer was lame, even for a 5day work week, nevermind 6day...
I took a different job in Austin (higher start salary, lower cost of living, and a 5day work week). Have never regretted skipping out on their 6day a week slave job (especially in 2001 when the market crashed and their stock options went to crap before they even vested).