Both of my boats are trailer launched. Normally it involves two people. The procedure is simple. The ramp I use has a floating dock down one side, so the first step is to bring the boat along side the floating dock and tie up. That is often the hardest part because the wind is normally blowing you off the dock. Once the boat is on the dock the trailer is backed in and the two of us walk the boat onto the trailer. Once the boat is in the right spot on the trailer and secured at the bow, one person slowly pulls the trailer forward while the other keeps the boat lines up astern using a combination of a boat hook and a stern line. Alignment of the boat is critical particularly if you have exposed props and shafts. For my deeper draft boat (5') we have to disconnect the trailer from the truck and let it out farther into the water on a cable to get it into deep enough water.
Launching is easy. We back the trailer in until the boat is floating then I back the boat off.
Of course, we are using a Brownell hydraulic trailer. They make great trailers, but they are a bit pricey.