BMX - how do i get more height to my bunnyhop

ive been riding for about 2 years and at my peak i could only get about 20".
i havent been on a bike in 9months and im getting back into it but how can i get more height.

lift weights?

i dont think thats the problem i think theres a flaw in my technique

http://cache.jalopnik.com/assets/resources/2007/05/Stiletto_Heels.jpg

suck your legs up real far?

Post a video of your 20" bunnyhop technique and we'll critique it.

Practice.

jump over someone kneeling at about 23inches then you have no choice but to make it, unless you want to hit your friend in the face with your bike. no for real though, just tuck in lift up towards the sky until you cant anymore then push forward and lean back so that you are nice and tucked.

Its all about weight tranferance. This is for an "American"( I invented this term, but thats a differnet story! Very,very old skool). Its easier to do well if going very slowly. But in theroy if you can make the same weight tranfer when going faster it should give you more energy and more height.This is what you need strenght for.else its all about technique. Basically you need confidence, as you are going to go from extremes of weight tranference very quickely and excellent timing to get a few more inches.Be brave and pratice on grass!

1.Make sure that the pedles are well set. Start as high as you can go then go as low as you can by bending knees and elbows .
2. Pull up, and back on the bars as you go up to a standing postion,you should be over balancing here and falling backwards if you are trying hard enough.
3. Your weight should be thrown to the front of the bike deserately trying to counterbalance the bike from fliping backwards with the bars pressed in to stomach.bend head/stomach over the top bar to allow even more counterbalance.
4. now push the bars forward bend the knee and sit on the back wheel, or even behing it if you can. This corrects the bikes balance. Once under the bars push forward and upwards to gain some more height. If you have got this right the wheels should now just be level with each other in this tucked as far back postion. As soon as you untuck your body from sitting on the rear wheel for landing the rear wheel will drop very quickly ,and again you should have a real battle stoping the bike flipping backwards before you land. If you have commited enought to it you should be landing rear wheel first .You should only just be able to avoid it flipping backwards again on landing.ie you end up with the bars pressed in to your stomach again on landing!

If you have really got air off a ramp using a bunney hop, slowly stand up again so that you dont push the bike downwards , and tuck the bike in to your body again! IF you have used enought force you should still be going up at the first tucked postion, the second tuck does not really add height it simply pulls the bike up slightly, which gives more air.
hope this helps.