I've been skateboarding for years and whenever someone wants to learn how to do a kickflip I explain these simple steps.
1. To begin with, you need the toes of your back foot on the tail of the skateboard ready to pop, and the ball of your front foot just behind the front bolts.
2. Angle your front foot out slightly, so you feet make a V shape.
3. Bend your knees and pop the back of the board, just like you would in an ollie.
4. Now with your front foot, move your foot up the board like you would for an ollie, but also flick it to the side. This will cause the board to spin.
5. Pull your legs back directly above the board and catch the rotation, keeping your feet over the bolts (I once broke a board landing in the middle)
6. Land it like you would with an Ollie, and keep skating.
With these simple steps you will find it very easy to learn how to do a kickflip. Just remember to wear safety gear on your first couple of tries.
I mentioned in the steps above that I once tried to do a kickflip, but I snapped my board. The board was a couple of years old and I had grown up a bit, you need to make sure you have a good board when you move into tricks like the kickflip. Soon you will want to do stairs, and rails, and then you really need a better board.
You also need to make sure you have the right shoes and stuff. As a joke I once tried to do a kickflip with bare feet, man it rashed my foot up pretty badly!
Cheers guys - rock on!