Tabletops and Doubles. Start your jumps here and work up to doubles. Speed is key to taking off as is controlling and planning your landing. Wear as much armour as you have whilst learning. Crashing hurts. 

1) Coast in a neutral position. Centre yourself over the bike, arms and legs slightly bent. Pedals level
2) Crouch down as you approach the jump. Bend your arms and legs to lower your torso
3) Your crouch should be at the lowest point when you reach the bottom of the face (front tyre just on it)
4) Begin to spring up as you go up the face
5) Push down with your arms and legs, pushing the bike into the face. For max lift straighten your arms and legs all the way as you reach the lip
6) As you leave the lip bend your arms and legs to let the bike rise up into your body

(rider Ian Peake)

Land rear wheel first on the top of the table top but not too high or the front will slam down
On a backside you should aim to have your front wheel touch down then the back wheel to land in the same place. (obviously not at the same time)

Wear as much armour as you have while learning. Crashing hurts.