thats comepletely vague.
1. Ride along at a reasonable speed (It doesnt matter
how fast really)
2. Lift your front end up, the higher the better.
3. When your front wheel arrives at a decent height
(usually a few inches, but high enough to clear the
box or whatever you might be bunnyhopping over)
pull your handlebars DIAGONALLY FORWARD/UP. This
will bring your back end off the ground
4. Practice getting higher by tucking your knees into your
chest when your off the ground
This is also known as a wheely-hop