I just got back from Bali.  One of the ways I lowered my costs was to buy food & alcohol in the supermarkets.

There wasn't always a large market available, but even the small markets offered food and drinks at a much lower price compared to within the restaurants and bars.

Too many people think they need to eat each meal at a restaurant when they are traveling.  This will add up very quickly and will also pack on the pounds.  It is so easy to get some granola bars or fruit at a store instead of paying for a more expensive breakfast at a restaurant.  There are a ton of options for a cheaper lunch while traveling.  I usually would go to a restaurant for dinner, but I would seek out good value restaurants on the side streets away from the main tourist areas.  

Drinking at bars is expensive.  Remember in college when you figured out that having some drinks at your place before going out the bars was a nice way to lower your costs?  The same is true on vacation.  I bought cold beer at a local market and drank it on my hotel room balcony.  When I went out, I would have an expensive beer or two at the bar, but that would be all I needed.  If the public drinking laws are lax, you could have a much cheaper party on the beach with the stars and moon above instead of sitting in a bar.

If you want to be a good budget traveler, you need to find ways to cut your costs.  Buying food and alcohol at the local market instead of at the bars and restaurants is a great way to save money while you are on vacation.