A beaching bumper like Hamby's or Keelshield makes launching a boat by yourself a breeze. Like others here, just attach a rope between your trailer and boat, back down till boat floats, then pull the trailer out of the water. The boat follows and beaches itself on the ramp while you go and park the truck. I found I tied up the ramp less doing it this way, then motoring over to a dock while my trailer sits in the water. After someone slammed into my boat while it was tied to a courtesy dock once, I find my boat is much safer beached on the ramp than tied to a dock.