Im kinda doing the same as you and my coach gave me two drills to work into me.
1. lie flat on your back, this can be done holding onto a bed or starting clean,
Bed - place your hands under neath your bed or some kind of ledge so that you have grip. Then whip your knees up to your head by lifting your hips off the ground. Make sure you leave your shoulders and well upper body remaining on the floor.
Starting Clean - Same idea as above but you want to first whip your arms up to your ears, (you can place a pillow or something above your head so your know when to stop your arms) and once your arms hit you then lift your hips and knees like above.
Preferable work on the first one then the second one and do as many reps as you can to really work your muscles.
2. This is basically a tuck jump but you have to make sure all your technique is correct. So start standing clean as if you would do for a tuck but make sure your on some sort of line. Then set and push off your toes and up and be really aggressive to get as high as possible. Make sure your whipping your arms up and hitting like in the other drill. Once your as high as possible then you lift your knees to your chest but DON'T GRAB! leave your arms up till you finish the jump. Sounds simple right? once you understand what your doing now you can really work on technique, so ask yourself.
1. Did i land back on the line?
2. Was i aggressive at getting a higher jump?
3. Did i pull my knees to my chest with my core not my arms?
4. Was my timing right so that i got enough height before i tucked?
If these were all yes then your tuck should be much better :)
Just remember a tuck is an upward motion hitting then a backward rotation motion hitting, and think more about your knees hitting your chest and pulling you over with your arms there to make it look pretty instead of trying to pull your legs to your chest with your arms :) Its all in the CORE!!
Let me know how this works for ya :)
Good Luck
