Do a Bronco

This article teaches the most basic yet most important trick in BMX

Steps

Ride at a speed you're comfortable with.
Lean back and pull up your front end without bending your arms much into a very high manual (ensure you lean back and not just pull it up whilst leaning forward).
Throw your weight forward and "scoop" your back end up off the floor to level out.

Be comfortable with "flipping" (coming off the back and landing on feet) a manual first to gain confidence to lean back far enough.
If you're landing nose first, lean back more! (sounds stupid but is true).
If you're struggling to get back wheel far off ground then push your bars forward when throwing weight forward.
You CAN (and will) hop higher over things than on flat. Try it (within reason).
To improve height just lean back more. The higher the front, the higher the back.
Start off with road lines, then a branch, then a curb, a skateboard, 2 skateboards, etc.