You don't HAVE to sand, although I think it often looks better when it's sanded first, and it does help the paint adhere better.
You do need a primer though, and if you are painting it black you will need a dark base primer. Ask the guy at the paint counter which would be best for black. I used a brown primer on mine.
Personally, I like latex paint because it is easier to work with, but some prefer oil based because it can adhere better to wood.
Enamel is another good choice. It is very durable and has a high gloss, but is also more expensive. I have found it at Big Lots though for a good price. As long as you use an appropriate primer for whichever paint you use, it should be fine. You will probably want a gloss or semi-gloss paint since flat paint tends to scratch off or get marked really easy.
Anyhow, just be sure to fill in any holes, cracks, etc., sand if necessary and use a good primer. As long as you aren't using flat paint you probably won't need a top coat or sealant.
If you frequently spill liquids on the table(and they sit there for awhile), or have hot objects directly on the table, I would suggest skippind the pain, and stain it instead. In that case you WOULD have to sand it completely, and apply a varnish or sealant after the stain, but it would be much more permanent and durable. You can get wood stain in black (or ebony), although it may take two or three thin coats to get it to the darkness you want. It may also take a lot longer, and will HAVE to be done outdoors as stain and varnish have much more fumes.
Any other painting questions, fell free to drop me a line!