Got back from my trip(my 4th time) to Tmn Negara and I don't mind going again in near future. :). I went with Tahan Holidays and here are the standard itineraries for a 3days 2nights stay.

- on the first night after dinner, you will be viewing the Introduction to Taman Negara at Interpretive Center and then head on to the night jungle walk. The walk will take ~1hr and the guide will usually bring you to the Tahan Hide which is the nearest. Be prepared to see some interesting insects.

- on the 2nd day, you will be hiking up to the Bukit Teresek and on the way down, you will get to enjoy the canopy walkway which is the longest in the world. You should be hungry by then, hv ur lunch and then head on to Gua Telinga(Ear Cave) by boat. The cave tour will be ~1hr depending on the traffic inside the cave. Some part of the cave is small/tight, so, if you are big sized it's not advisable to go in. Be prepared to get dirty.
After Gua Telinga, you will be heading to rapid shooting and this will get you all wet. Good to wash away all the guanos on you. The orang asli settlements awaits you after the rapid shooting. See how they make fire and use the blowpipes.
Dinner and u r free for the night.

- on day 3, you will be heading to Lata Berkoh which is a cascading waterfall. Nice to take a dip here, but beware of the strong current in the middle section. You will be stopping at the Kelah Fish sanctuary, nothing much to do here. Lunch and good bye Taman Negara. :)