If you're out during the day, then two kittens are a really good idea, as they will spend a lot of time chasing each other around rather than trashing the house. But cats are by nature solitary, so if you are at home to keep an eye on what they are getting up to, then one on its own would be fine. Kittens need lots of things to amuse them, otherwise they will start making their own "entertainment", e.g. climbing up and shredding curtains, like mine did when he was little. So it's a good idea to have plenty of toys - mine loved playing football with wine corks.
A good website is the Feline Advisory Bureau:
http://www.fabcats.or...ers/kittens/index.php
Expect a bit of naughtiness and wanton destruction, though - that's all part of a kitten's charm!