The first golden rule for an independent budget traveller to heed is quite simple: travel light. Its importance can not be stressed enough but often this adage is only learned through experience. It often seems that the best time to pack for a trip is immediately after the lessons received on the previous one, when you know the items that were essential and also the ones that were rather pointless.
When packing, make your primary consideration the climate of your destination and focus your packing on practicality and weight. Generally speaking, the less developed your destination and the more you will move around, the more important it is. Conversely, the more developed your destination and the less you will move around, especially if you have your own transportation, the less important it is. Either way, get into the habit of carrying only what you need and no more.
So what are the actual reasons we should travel light? If they could all be captured in a single word, it could well be 'mobility'. A smaller pack makes you less cumbersome. You look less like a tourist and receive less unwanted attention. It will make using transport like motorcycles, rickshaws and crowded public buses much easier. Often you take it on a bus with you instead of it bouncing around on the roof or in the luggage hold underneath.
A light pack enables you to walk freely for longer distances and also quickly if you need to get away from touts or undesirable locals. It can sometimes eliminate the need to take a taxi. If there are no storage lockers, it also makes visiting an optional destination en route much easier. Even if lockers are available, sometimes a large pack can be difficult to fit inside, meaning you'll have to separate some items and pay for a second one.
Even for someone in good physical condition, carrying a heavy backpack can exhausting, especially if it is hot. It can contribute to travel fatigue and a less enjoyable trip. The balance between the convenience or comfort of those extra items and having to actually carry them usually just is not worthwhile. Bear in mind that your backpack usually gets heavier with souvenirs and gifts as your trip progresses. That's an even stronger reason to begin your travel as light as possible.
Another good incentive is that many airlines now offer cheaper fares for no checked luggage. If you are on a shorter trip or otherwise feel you can travel with only a carry-on bag then take advantage of this. Travellers who can fit their backpack into the overhead locker of a plane or neatly under a bus seat are probably the most free and happy. Although they are sacrificing clothing choices and other various other items, their reward is an enviable sense of liberty and manoeuvrability.
While that option may be a little extreme and probably for most, there is certainly every reason to keep your backpack light. Everyone is different and establishes their own list of 'essential items' through recommendations and often more profoundly, by experience. They say that the best time to pack for your next trip is immediately after you've finished the last one. It makes sense because you'll remember that if something falls into the 'I may need it' category then you'll leave it at home because in all likelihood, you probably will not.