Great island, so much to do and see. Definitely rent a car which you can do cheaply.
Definitely visit Sarakino whatever you do. Fantastic place with most incredible landscape ever. Papa Fragas and Mandrakia (i think) are definitely worth a trip too. Paleochori beach is great.
- Eat at the Aragosta restaurant in the port. Ghastly place with vile food and is triple the price of all the lovely tavernas. Seriously.
- Visit the Katacombes that you'll see signs for everywhere. They are pathetic! One small cave room and so uninteresting.