I ought to do the same but I've been putting it off because it seems so hard. Here's what I've heard:
Remove doors and hardware
Wash well with TSP
Sand lightly
Use oil based enamel for best hardness (latex is not as hard, but is much easier to clean up)
Spraying would be better than brushing (no brush marks) but who has a sprayer?
Do a few coats, don't rush
Let dry really thoroughly before reattaching hardware
Avoid painting shelves - use shelf paper instead
If you do it - do it properly!! We did our kitchen cupboard doors last year and over the months the doors got so chipped we ended up paying out for some new doors anyway this year.....it takes lots of effort and they can even get chipped just putting the doors back on.
Might be an idea to varnish over the top of the paint to stop any chips or knocks occurring.