The biggest key is what Tuneman said - make sure you are completely in the air before beginning your rotation. If not, you will get pulled off-axis and it will be very difficult to land the trick.
As for the handle pass, you want to make sure to make it in the "small" of your back, which is basically your waist. This is what they mean by keeping the rope low. You also need to make the handle pass right next to your body, as it is the easiest place for your other hand to find the handle on a consistent basis.
What worked for me was tying a rope to a tree and practicing the handle pass and rotation. This way it will be natural when on the water. Make sure to keep your hands in the same place on the handle as usual going into the wake, then when you go behind your back, you will flip the handle, going from palms down to palms up. When your other hand grabs the handle and you spin back forward, the handle will flip again and you will again be palms down.
You will find that if you can make the handle pass halfway through the trick, the boat will pull you the rest of the way around. This is the same with the backroll. So, if you can rotate halfway and concentrate on the handle pass, you will start landing them.
Get on the forum over at kneeboardplanet.com. People are very helpful with things like this.
Best of luck.