Avoid hanging things all over the outside of your pack, you will be making irritating noise along the trail and the vegetation will snag your things. If you have to hang things outside then maybe your pack is too small. You don't dig out your whole pack just to look for your lunch pack or water, keep your rain gear or medication in handy places. If you create garbage along the way, have a plastic bag handy so you will not be tempted to throw them away. Make sure your liquids are kept in watertight containers and have no chance to leak even if you have a fall.
Plastic bags are important.
Put all the things you need dry in a large plastic bag and as security measure put the bag into another bag. Tie up both bags separately and tightly after pushing out all the air. This is in case of accidental puncture. It can rain very heavily in the jungle and the only way to keep your things dry is the plastic bags. Sometimes you need to do river crossing with your packs and you may be wading up to your chest in water.