Get a spot first and foremost! They can show you what it's supposed to feel like to do a correct layout on the floor. (Not too much spotting though...you don't want to become dependent on it!) The rod floor is the next "on your own" step, so try to get it on there if your gym has one. After that, try tumbling from the spring floor into the pit if your gym is set up that way. That way if you fall, freak out, land funny, etc, you won't get hurt, mat burned or bruised. It's definitely a confidence builder because if you can land it perfect in the pit, it's essentially the same thing on the floor, just without the squishy landing. :)
I worked on layouts forever and have had every issue with them you can think of. But I perfected them and now I have my full! Here are some tips that really made a big difference in mine:
1. Tumble FAST. That just doesn't mean running fast. The main thing is to leave your hands on the ground for the shortest time period possible. You want to snap from your open body to hollow body as fast as possible in your round off and back handspring. This will give you your energy for the height of your set.
2. When you set, block at a 2 o'clock angle from the ground for maximum height. If you land your back handspring straight up and down to the floor (12 o'clock), your momentum is going backwards from your back handspring so your set will fly back and your layout will most likely be whipped. This helps with tucks and fulls as well!
3. USE YOUR HIPS. This one is the hardest to grasp! You are basically supposed to pelvic thrust in the air to prevent piked layouts. Try to push your hips in front of your shoulders and squeeze that butt like it's your job! It'll feel awkward and your instinct will tell you to pike and drive your feet to the ground, but instead drive your hips to the wall in front of you and let your feet land meanwhile.
Good luck!