I found this helped me a lot: (please don't flame me, I admit I am still a loop noob, this is just what I found helped me)
Keep steering the kite in a fluid motion all the time - by this i mean, dont stop it turning, or slow down the turning. I previously spent a lot of time boosting, then stopping the kite at 12 (or even redirecting it back a bit), and then near the apex, steering it again to do the loop. However, it never felt good and often had really heavy landings. It was only when I started ensuring that the kite always continued moving in the direction of the loop, that it started to feel 'right'. It was the 'continuous movement in the direction of the loop ' that was key for me.
So, I send the kite up really quite slowly, and tend to leave the water well before it reaches 12, and then just as it goes past 12, start to tighten up the turn more. Give it a try sending your boost really really slow, leave the water earlier than you'd think, and keep the kite going round (because it's slow, you have plenty of time to watch it in the air), and then when it feels 'right', start to crank the bar in harder.