When hiking in the Malaysian rainforest, whether a simple jungle walk or to climb the highest mountain, some simple principles that gets you acquainted with exploring the tropics apply. Light clothing is the order of the day as it is very humid, but if you happen to hike in higher elevations or the highlands, it goes without saying that thicker apparel will be useful. If you don't have expensive hiking shoes, construction boots or rubber shoes (can be gotten from a hardware shop) are good and cheap alternatives. Slippers can be used for flat trails but are not recommended for steep inclines, especially if it gets muddy after rainfalls.
If you're making a long trek, bring along sufficent water. You should bring along a portable torchlight or head lamp if there is the slightest possibility that you may be late out of the forest. It gets very dark quickly under the jungle canopy when dusk approaches, and the last thing you want is to lose your way on the trail. Leeches are a common feature of the tropics in Southeast Asia - bring along some salt if you're squeamish. An insectide called 'Baygon', when applied sparringly to your foot gear, used to be able to ward off these creatures, but it is no longer effective with the change in its new formula.
If you ever happen to get lost in the forest, pray that you will find a stream nearby. Follow it downstream and it should lead you somewhere. Most of the gazetted parks have trails that are marked with ribbons or plastic strips tied to tree branches, shrubs, shoots and vines, so keep an eye out for those if you can't find seem to find your bearings. If the park has an office, do make your registration so the rangers can come look for you if you don't get out after the appointed time. Stream water is drunk by the Orang Asli (Aborigines) without reservation, but you shouldn't do it unless your stomach is used to it or if you are dying of thirst. In this case, remember never to drink from stagnant pools. Lastly, unless you are travelling on a well-beaten path, you should always have an least a friend with you on your hiking trip. The more, the merrier but in this case, safety does come in numbers.