From Lonely Planet 2010:

- Phuket high season's around Xmas, NY eve & CNY, so do book a room at least 3 weeks before during such periods.

- Check agoda.com for last-min deals & availability.

Useful websites:
Phuket.com
jamie-monk.com
bangkokpost.com or nationmultimedia.com

Read Alex Garland's The Beach.

Stock up on sunblock which is expensive in Phuket