Do try the local food be wary of ice cream and avoid the macdo !
Try and talk to the locals in their language even if you start by asking if they speak English its better than just starting to rabbit on in English.
Check your bank charges for getting cash out, here is one of the best guides Nat West need to be named and shamed ! But there are others...
Clean out your wallet when you head out - you might not need to carry your cards on you, at least not all of them. There is a small chance but a bigger one than here in the west that you may get asked for all your possessions. I advise if you can to take a crappy digital camera and between you and your friends have enough cash across a few pockets to get you back to your hostel safely.
Try to smile if you get into any bad situation, people don't usually want to harm you its just your valuables they want again, don't go out wearing bling. Hand over the lesser amount that you stashed and back away.
Try to be businesslike not show fear - get the point across that you are giving their 'tax' and do it quickly.
Your hostels should have safety deposit boxes, take small padlocks with you to take advantage, often travel theft is from your own fellow backpackers though it's not common.
Check if you have an old sim free phone you may be able to get a sim in the foreign destination. There is NO cheap way of using your own network contract abroad anywhere ! Really think twice about taking your great smart phone out on the town or even with your trip as a whole.
Backup your photos to CD or laptop (or flash drive etc) if travelling with one, if you are be wary of where you are when you take it out. Don't flash a laptop/tablet around if you can help it.
Forget all of the above your excitement and instinct will take over anyway :)
Please post your travel tips below if you have any more.