I just posted a short video on painting kitchen cupboards doors and cupboards. In short if you have a standard set of kitchen cupboards made from either wood or melamine covered they can be painted.
The first step in painting kitchen cupboards would be to remove all the hardware such as doorknobs and the door hinges. But before you remove the door hinges I would strongly recommended that time to totally wash and degrees all the cupboards outside. This will make painting them much easier. I usually use a soap such as dishwasher detergent or some type of spray bottle degreaser from your local box store. Clean all your cupboards down and then wipe with a dry cloth. If you feel comfortable with painting around your door hinges then you don't have to remove the doors which will make it easier to paint because you don't have to move around your doors you just paint them in place what on the other hand if you can't paint properly around your cabinet door hinges you will have to remove the door.
Now that all your doors and cupboards are clean and dry the next thing to do is to give them a sanding with a finer grit paper such as 120 grit to 180 grit, this will keep scratches to a minimal. Scratches to show up through paint when you're painting doors that will be quite visible and close to the eye. I usually use a block sander to sand the flat surfaces. Then I use a sponge Sander to sand all the contours, this gets into the nooks and crannies of your contours. Then I wiped the whole thing down with a damp tack cloth (this cloth usually is a clean white cloth slightly dampened with varsol).
After everything is totally and completely dry you're ready to apply a quick dry primer. Priming should be done very sparingly not to over pack the cupboards with access paint. The whole idea behind the primer is to have the paint stick to the primer since sometimes the paint will stick directly to the bare wood. Then when the primers dry approximately 24 hours later and very light sanding is in order again using extremely fine sandpaper not to start scratching and scraping the primer off. Again I will take it lightly dampened tack cloth and wipe it down again. Once dry your ready to paint.
I advise to do multiple coats daily applied every time to ensure a nice smooth even painted surface. Do not try to paint to finish in one or two coats. Sometimes the second coat will definitely cover but if you're using a darker paint you might need three coats to get a nice smooth evenly coated paint job.