First, you'll need to clean the formica, then 'rough it up' with some sandpaper for the primer to adhere. Then, you'll probably want to use a bonding-primer or perhaps a primer that's 2-part epoxy in formulation.
The best thing to do is visit your local Retail Paint Store (found in the YELLOW PAGES under PAINT - RETAIL.) Buy good material and tools for this job, unless that is, you're a masochist and LOVE to re-do formica cabinets.
Personally, I'm not a big fan of what you want to do. If the job does fail, you'll have paint chips in your food (assuming you have cabinets hanging above your working countertops.) Then, you'll and up doing what I prefer - Cabinet Refacing. That's right - It's what you see advertised on TV at 2am in the morning. It's inexpensive but certainly a LOT less than NEW cabinets and a bit more than painting them. Refacing will certainly look nicer and more professional. And if you're planning on moving in a few years, it should add decent value where you'll be able to recover the costs. (Just try to stay 'neutral' with your color selection if you're planning on moving.) If you're planning on staying for many, many years, certainly pick a face that's YOUR taste.
Other than visiting your paint store or pricing a refacing job, I haven't much more to offer. Do realize that a Paint Store will 'encourage' you to paint your cabinets. It is their business to sell you paint; not sell you on how well it may last or look or whatever. My best to ya and hope this helps.