The Ollie is the basic trick in skateboardin'.
Get familiar with ollie before you start to do any other tricks.

Here's what you do :

1. Ride with moderate speed
2. Place your front foot on the middle of the board,your back foot on the tip of the tail.
3. Remember to place your front foot properly or you won't be able to do the next step successfully.
Now bend your knees to gain power.
4. At the same time,pop the board with your back foot and
jump while you slide your front foot towards the nose of your board.
5. Touch Down.

Tips for beginners : In the whole process of step 4, it's all about the guts, the thing to learn before all these shit is to have no fear, from now on, whatever you do, just take a deep breath, shut up and do it.

Tips for all of you : Always remember to suck up your knees when you're in the air, it's gonna be easier to jump over things, and it allows you some time to do add-ons.