The fastest way to get a cat to be a lap cat is to ignore them, seriously!
What works best is to sit down on the floor with a book and start reading out loud softly (this stirs a cat's curiousity. Have some treats set out in a circle around you, and have two on your legs as well. When the cat comes up, keep reading, don't make eye contact at all, just ignore him. Let him climb all over you, don't move a muscle, if he head bumps you, as hard as this is to ignore, ignore it. Do this for about a week, twice a day if you can. At the end of the week, you will have this cat craving for your attention, and wanting to sit on your lap. When he does finally sit on your lap, only pet him once of twice then quit. Some cats don't like to be over stimulated, and petting is stimulation for them. Remember, petting a cat is what we *need* some cats could care less about it, and others can't get enough of it- it depends on what is lurking in their past- life experience-wise.