Often it depends on the kind of trailer you have and the conditions at the launch ramp you choose. In addition to the information already posted for you here's one of the ways I launch.
I get the boat ready (check that drain plug of course). Get all my gear on board.
Back the trailer down the ramp to a spot just before it starts to float. Put a stern line on and tie it to a dock post with some slack. Also a line on the bow (or mid cleat) depending on your trailer, boat and the ramp.
Back the trailer down a little more, slowly. The back of the boat will start to float. I give the vehicle
a little jerk by quickly applying the brakes. The boat usually floats off the trailer and is held in place by the lines I've placed.
Again it depends on the ramp and how crowded it is. I may move the boat and then park the trailer or tie the boat better and then park the trailer.
If you have any doubts then feel free to ask another boater for help.
The real question is, why can't you get your wife or significant other to get in the water and do the launching? 
Good luck and happy boating