I'm guessing you're starting on an older kite, they aren't meant to be rock hard (ie giving that hollow ping when flicked) like newer kites. They aren't made for the higher pressure and won't really go as firm even if you pump the hell out of them - all you will do is end up blowing a bladder or even the canopy.
If you're using a 2nd hand kite i'd stick with the old 'baywatch firm' rule...

A bit of flop might make it slightly harder to get off the water, or a bit more 'flappy' in the sky (that's the technical term, aka jellyfishing) but at least your kite won't go pop when you smack it down fully powered up. Which you *will* do a few times getting up on the board.