At first glance, launching a boat from a trailer looks like a simple procedure. But, anyone who has tried it knows full well that it takes some practice to back up to the ramp, drop the boat in the water and them scramble to get out of the way of the next guy. There are three phases. With practice you can easily master the pre-launch, launching and retrieving a boat but it does not come automatically.
Boat trailers come in a variety of configurations. They do have some things in common. There is a winch post and winch. Most have fenders over the tires, and most have submergible taillights. If the taillights are not submergible disconnect them prior to backing into the water and reconnect when taken out.
At the ramp, before you actually launch, it is a good idea to pull off to the side. Transfer gear such as coolers, fishing tackle and safety equipment to the boat. Make sure you have at least one Personal Floatation Device (PFD) for each person in the boat. Later make sure everyone wears them. Install and/or tighten drain plugs. Check batteries. If necessary hook up and pressurize fuel lines with a couple of pumps of the primer blub.
Next check the ramp itself. Look at how steep it is and how deep the water. Is the ramp slick or dry? Is there a dock where you can tie up? Or will you have to beach the boat after launching?
Returning to the boat, remove the tie downs. Be sure to keep the bow winch line attached to the bow hook. Make sure there is at least one docking line attached so that the boat is controllable once it is afloat. Two lines are better as they afford better control over the boat once it is in the water.
Before launching, raise the motor so that the prop and lower unit will have ample clearance as you back down the ramp.
Phase two is the actual launch. It is best to allow the most experienced person in your group to back the trailer down the ramp. It can avoid damage to the boat and/or trailer from unseen obstacles. On a multilane ramp, be sure to remain in your lane. Link to complete tip – https://dongasaway.wordpress.com/2016/04/18/how-to-launch-a-boat-with-ease/