I'm still learning and I am fairly rubbish
But
it helped me to practice on a high curb
front wheel up (by shifting weight back and pushing forward on pedals)
then let the front wheel touch the top of the curb
then quickly shift weight forward, and push bars forward whilst unweighting your feet (point toes down to help with this)
if you are doing it right your back wheel lifts smoothly onto the curb
do this quicker and quicker – then move on to hopping small bits of wood etc. The change now is that you are trying to lift the back wheel whilst your front wheel is in mid air and not sitting on a curb