Great point. I'd recommend the book "Consider your Options" when you're accepting a job with stock options: http://www.amazon.com/Consider-Your-Options-Equity-Compensat...

It can be dense reading, but no one cares about your money more than you do, so it's your responsibility to make sure you understand what's going on. Doing that research saved me making more mistakes down the road.

Another common mistake with pre-IPO companies is to say "Wow, I get X thousand options!!" But you have to ask how many outstanding shares the company has. What really matters is what percentage of the company (your shares divided by total outstanding shares) is being offered to you.