Instead of buying one packet of chips from a vending machine or store, buy bulk from a super market or online.
This saves a lot of money!
When going to a venue(sporting game etc.) bring food and drinks as usually the price will be ridiculously high.
Change your own cars oil. This doesn't take long and there are a variety of guides and videos online on how to do it.
When purchasing an item, think whether or not it will still be useful in 3 years. This stop you from buying stuff like the shake weight etc.
When needing battery's it is always cheaper to buy a bigger battery and hack them like this!