Can someone point me to a good guide to stock options? I've been with a large company since graduation, with Restricted Stock Units granted to me, vesting over

Can someone point me to a good guide to stock options? I've been with a large company since graduation, with Restricted Stock Units granted to me, vesting over time as a nice bonus now and then. But in January, I start with a start-up, and I'm going to learn the reality of how stock options work first-hand. I'd like to know how to make sure I do the best I can with them.