I was practicing my casting this afternoon, and I made some observations. Try these tips; they improved my casting.
1) With the line straight on the lawn (or water) make a quick backhaul while pulling the rod behind you.
2) When you feel the line "tug" (with the hand holding the the flyline) start the foward cast.
These 2 steps do two things : They increase line speed, and create tighter loops!
It helped me. I experimented. Try it.