I'll dump my experience with the "theory" portion below, but the only way to really get the hang of it is to be able to have a car to practice with.
I learned over the course of about 4 Saturdays:
Week 1) Go to a big, empty flat parking lot. Malls late at night work great. Practice letting out the clutch VERY slowly until you can feel the car start to move. Do this for about 30 minutes. You'll stall the car a LOT. It's ok.
Week 2) Begin practice with just the clutch again. It should come back to you quickly. Once you've figured out where the clutch "catches", bring the gas pedal into the equation. You'll start to depress the gas pedal at about the time that the clutch begins to catch. You don't have to push the gas pedal far, just a be consistent in pressure. For a while, you'll hear the engine revving unnecessarily until you figure out how much you need to depress it, and when to begin. Do this about 45 minutes or until you feel you've "got it".
Week 3) Assuming week 2 has you feeling better about timing, another week of practice pulling out with clutch + gas, only this time in city driving (read: lots of traffic lights.)
Week 4) The hill. Stopped the car, parked headed uphill. Make sure there's no cars anywhere else on the hill, and it'll take a lot of pressure off. Practice pulling out going uphill. It's a lot harder, because the amount of gas you'll provide is increased. Believe it or not, you'll probably end up giving WAY TOO MUCH gas than stalling it... Oh, and you don't drift backwards anywhere near as quickly as you'd expect.
One note... all clutches catch at different places, and have differences in how "soft" they are. They also tend to change over time, so for even more experience, try someone else's clutch after you've mastered yours.