Agree with what everyone have said thus far.
Things that I did that helped me:
Go to a calm spot, no gas, no steering (centered) and only shift one gear lever forward for a brief second then back to neutral - watch how the boat reacts. Try reverse on the same motor - watch how the boat reacts. Keep experimenting until you know how your boat will react to different shifting combos. It only takes a little time to get it down and remember - go slow. I found it useful to drop an empty plastic gallon jug in the water and attempt to move the boat to it from different directions - you know, use the jug as the dock - no damage by hitting it.
I made mistakes in the beginning by rushing, using the throttles, staying in gear too long and starting too close to the dock when attempting to dock. Always stop in the water before you attempt to dock - watch what the boat does - is the wind making it move, is the current making it move?
Go slow - remain calm - you will be fine!