Each person has their own things that they feel comfortable with.

The way I did it was how a planned parenthood therapist explained it to me -

Some people start out by a quick touch of the fingers or hand. Others start by taking a bath by themselves and experimenting with what types of bathing supplies (bath oils, bubbles, flannel wash cloth or cottn wash cloth, ands so on) feel comfortable and nice.

Then as the person gets comfortable with being able to touch their own hands, arms and so on they move up to other areas experimenting with types of touches and so on by themselves that they feel comfortable with.

Then when they are able to pleasure themselves they move up to non invasive things with a significant other such as sitting on a couch together watching a movie.

Then move up to holding hands while watching a movie

Then a non sexual back massage with baby lotion or other favorite lotions.

And then basically move up to sexual things as the person feels comfortable.