Information is taken from http://www.klia.com.my the official website of KLIA

By Car / Rental Car
The usual large international car rental firms, plus local companies, are located at the airport. Car rental companies, including Avis, Budget, Hertz, National and Thrifty, operate 24-hour desks in the arrivals concourse, on level 3 in the main terminal. Traffic in Kuala Lumpur can be harrowing, so consider carefully before getting behind the wheel. Traffic should be very light on the expressways into the city but as soon as you hit the city, traffic grinds to a standstill during rush hour. Driving in the city is not for the timid and consider using the ultra-cheap taxis for transportation around the city.

By Bus
Public buses operate on a 24-hour basis. Three specific routings currently in place are Express Bus Service, Stage Bus Service route 1 and 2. The KLIA Bus Station is located at the Ground Level of Block C of the Covered Car Park. Trips to the city by bus could take up to two hours in heavy traffic albeit the ride is a very comfortable, air-conditioned one.

By Taxi / Limousine
It's available 24 hours/day. Coupons for the limos can be purchased at transportation counters in the arrivals hall. Take a cab directly from the KLIA Airport via the KLIA Expressway to KLCC in 60 minutes.

By Rail
Alternatively, you may want to take the KLIA Express subway from the Express Rail Link and stop at KL Sentral station in 28 minutes. From there you can take the Putra LRT and stop at KLCC station.