a few more words of advice i did not already see offered:
- have someone stand behind you an hold the seat post for you for a few minute to get you started
- at first, keep your hands in the middle of the bars, next to the stem. It helps you from over-correcting yourself right off the rollers
- when you need to stand up while pedaling (and after 15 minutes you'll need to briefly stand while pedaling), shift your weight backwards a bit to keep the belt from slipping that drives the front wheel
- when you stand up and pedal, don't rock yourself too far forward/backward or you'll ride off them.
- I found it helpful to watch the front wheel, or have a mirror to watch things a bit. Someone else posted not to. Find out what works.
- be smooth. everything's gotta be smooth. rollers will make everything smooth.

I really enjoy rollers at the beginning of winter. And I really hate them at the beginning of spring. They make you a smoother rider all round - straighter line on the road, smoother in a paceline, smoother pedal stroke. People you ride with on the road will appreciate, some will even notice.

Enjoy!