Practice your trailer backing in an empty parking lot to get proficient at it. It will save you time and grief at a busy boat landing. Load all your equipment in the parking lot not 1/2 way down the ramp that also allows you to double check everything. Make sure the key is in the boat.
Yep. I was coming to say this. Practice at least 20 times. Or go to a boat ramp that is slow.
Also, pick a boat ramp and a time where there are no boaters. Practice pulling on to the trailer often. ALWAYS be willing to back way up and run at your trailer. Do not be afraid to back up far to get a good start.
You will also find that you will back your trailer too far the first couple times. Remember, when getting the boat off the trailer, you want to float the boat. When putting the boat back on the trailer, you have momentum on your side, so you don't have to put the trailer back as far.
Learn and understand basic etiquette but find empty boat ramps until you're comfortable. Don't have your first time on the water near a busy ramp on a holiday weekend or something. Pick a night in the middle of the week.
Another thing....have a routine and NEVER break it. Drain plug...check! GPS....check! Battery jumper....check! A good routine leads to never forgetting. We once broke routine and I parked the car while my wife held the boat. I forgot her BRIGHT BLUE purse, which not only means we forgot her fishing license and CC for gas, but we can back to find it was a nice visual for the scum of the earth to break the window and steal her wallet. All because we broke routine once.