Hi Gemma, how are you?
You might have already now about this, but i would check out...
Just in case you havent. Got some good tips for British travellers.
I can only offer some tips I was given, such as never accept the offer of a taxi from someone in the foyer of the airport - always look for the official taxi rank, even if you have to queue.
Also watch out in the Airport, a couple i met got hit by an X-Ray scam. They put there hand baggage through and some one pushed passed them and went through another metal detector, they didnt wont to be rude and security let them through first, the guy simply collected the couples luggage, including their camera and got away with it.
Thats the bad stuff over, the CAMERON highland are amazing, really worth seeing, also Malaysia's most recognizable landmark, the Petronas Towers look amazing at night. If you like art, the gallery in Kuala Lumpur is cool too. There is also a Taman national park which, if you like the out doors life is great too.
A good guide book always works a treat while on the road, but i would get one while you are there, and I would not always trust a Lonely Planet.
Hope this helps, James.