take the tires off your wheels and jump up and down until they no longer resemble a circular shape
wtf is that going to do... brodie brat pretty much covered it... pull up as hard as you can in the front and kind of like push forward and down. Try it over some really small bumps or wheel chair ramps and then once you can do it on that try on flat
i dunno if you skateboard or not but its the same idea as an ollie. lean back, lift the front tire, push your body up with your legs,then move your hands up and forward and sucking your knees to your chest. it sounds confusing but it works for me.
For months I just totally couldn't get the back wheel off the ground, mostly cause I was practising the whole hop together. Try practising getting JUST the back wheel off the ground. Lean over the front as if you were gonna do a stoppie, point your toes down and pull up with yer legs, hips, to get the back of the bike off the ground for just a second.
you could also try twisting your bars forward, as well as pulling up with your legs, without pulling up the front wheel, just to get the back wheel up. when you get that just do the same motion right after you pull up on the bars. that's what worked for me...
You can try doing your hop over a speed bump so the speed bump hops your back tire up off the ground(like a cheater) just to get the feal. Then try to fully clear the speed bump for practice. This is from a Ryan Leech segment on Ride Guide so you might be able to find that clip for a visual.
it took a lot of practice before i got this but i started with the american bunnyhop which is where you lift up your front wheel and throw your weight forward really quick. then there is the english bunnyhop which i later did i do it by leaning forwards and kicking the back end up with my legs and my pedals angled, then the front end comes up naturally. Hope this helps but just keep up the practice and you will get it for sure!