It depends-do you really want to do it right?
If you want to do it right, then start by cleaning them with TSP (Trisodium Phosphate). Especially if they are kitchen cabinets that have been subjected to a few years of cooking grease/smoke and finger prints, give them two cleaning passes with TSP. Once they dry from the TSP sand them with 100 grit sandpaper.
Remove the doors from the cabinets and remove all the hardware. Make a rack so you can lay the doors flat so the finish coats will be as smooth as possible. The carcass can be left on the wall, but make sure you mask it tightly so paint doesn't bleed over to the wall.
The primer you use will make or break the finish. To get a smooth, quality surface, you need to use a high build sandable primer. The primer will fill the wood and even out the surface. It's important that it be sandable so you can smooth the surface before painting on the finish coat. Don't hesitate to put on a couple coats of primer. If you don't use a high build primer, you will see the grain through the finish.
The finish paint should be 100% acrylic, however check with your paint supplier and see what they recommend. Take your time and use a combination of brush and roller depending on the door style. Brushing will let you get into the nooks and crannies, and a roller will produce a smoother finish. If possible, consider having the doors and drawers sprayed-spraying will produce a much smoother finish than brushing and rolling and isn't all that expensive.
