start off by holding your right left and middle splits for 10 seconds each.
first do a strattle and go down to your right left and middle
do bridges! this is me doing my bridge a while ago. they've gotton pretty crappy so make sure you do bridges every day!
try to hold good bridges for 10 seconds each! then you should be all stretched out and ready to go!(:
bridges definitely help to make your back more flexible and theyre an important step to getting a better back handspring!
before ever trying a back handspring on the ground.. you should be able to do a back bend kick over easily and fast(: it'll help! when you first start back handsprings use a soft mat and have a spot!
hope this helped!(: again make sure your bridges don't get as crappy as mine!;)