There is plenty of places where you can rent motorbikes, bicycles and cars. There is also plenty of places where you can hail a taxi.
To drive you need a drivers license. International drivers license says the law but my Swedish driver license is working just fine.
The motorbikes costs from RM 25 / day and cars from 50. Bicycles 20/day.
If you feel you don´t want to drive yourself there is plenty of taxi stands that will drive you where you want to go. The taxi prices on Langkawi is fixed so it doesn´t matter if you are one or three, same price for the same ride. The drivers are also avaliable to rent for a whole day if you want to and they will show you all there is to see. I think it costs RM 100/day .
Remember to drive on your left side and wear a helmet at all times!
Normally when the police are standing by the road wanting to check passing cars they will just wave o you to pass. They are not so interested in the tourists (as oposed to in Thailand where they are keen on getting some extra money from the phalangs.)
They stopped me once and I have been driving here for a year, but I believe they were more interested in the motorbike than anything else, kept asking me about it. :)
If you are here during the rainy season and are renting a bike or a omtorbike then remember to bring a rain coat and a plastic bag for the stuff that can´t be in the rain. If you are caught in the rain it will get soaked otherwise, the rain is normally very heavy!
Ok, now you got a ride, what should you do? Check [here] for a good listing of things to do.