It really comes down to practise. Make sure your comfortable on the bike, so that trackstands come easily. Build you confidence back hopping and just doing wheel pivots on curbs just so that your overall bike control increases.
To go bigger, make sure your really kicking the pedals, they'll give you the majority of the lift and the harder you kick the higher/further you'll go. Also, a bit more so for sidehops, remember to preload. Make your body go low so that you spring up, hopefully bringing the bike with you.
And try and be relaxed, it's much more difficult to ride when your tense. Be all loosy goosey