Have you tried converting to Heel Flips?  lol, Kidding.

 

Kick Flips.. seems like a lot people have more trouble on these than most tricks.  I usually have trouble with Kick Flips whenever I get a new deck with sticky grip tape.  A lot of this trick is commitment, and it sounds like that's what you're missing by what you said about landing them in the grass.  Picture yourself doing a Kick Flip.  First of all, does it look decent in your mind?  lol, Can you imagine yourself landing a proper Kick Flip?  Do you know what one looks  like?  These are questions you should be able to answer before you set out to perfect your Kick Flip.  Landing with one foot, whether it be the front or back is all from not committing.  You have to be ready to take the falls with the makes.  Otherwise, nothing is going to happen successfully.

 

Pop, then flick.  My buddy Mike has the problem with popping and flicking simultaneously, and it develops more of a roll than anything else.  If you want height out of a Kick Flip, you need to learn how to pop before your front foot leaves the nose and does the flick.  Take it slow.  Literally.  Pop.. then.. flick!  Jumping higher definitely helps with giving you enough air-time to allow a full rotation, obviously.  Also, I feel jumping higher is safer, too.  Gives you more time to think and see what's going on, instead of rushing yourself into another mistake.

 

Foot placement for setting up isn't really all that important.  You can get a Kick Flip from just about anywhere on the deck.  But, be sure to adjust with new foot placements to see where it works best for you.  Also, when crouching before any trick, try not to get too low.  Because that'll throw off your balance (unless its working for you then never mind, i guess).

 

Like all tricks, you get better from experience.  You gain knowledge of how much power you need to put into your flick in order to get the board to flip correctly.  But I'm guessing you have more problems with the landing, right?  You just have to say "fuck it" and plant your feet down, Man.  Wussing out on a trick can be more risky than not wussing out.  Landing with one foot on the tail can cause the board to catapult upwards.  And nobody wants that!

 

I could say, watch videos and slow mo them.  Just to get the technique down.  I do it all the time with tricks I want to learn.  But like I said before, if you can visualize the trick being done in your mind beforehand, you're that much closer to actually landing the trick.  Visualize, and execute.