One thing that will need to become like second nature to keep your living expenses down will be the ability to bargain or haggle. Unless the price is clearly marked, like in a supermarket for example, just about everything in Bali is able to be bargained on.
Many people aren’t comfortable with this practice as we don’t do much of it in our home countries, but it is the way of life for people here.
If you already have an even rudimentary command of Bahasa Indonesia then things will be easier as well, as you will be perceived as a little more "in tune" with things.
Just like anything else there are some rules and guidelines to go by to make sure you don’t get ripped off and don’t offend anyone in the process.