My tip for today is to make lists of what you need to purchase, and stick to the list!
I have a notebook where I keep a running to-do list for myself. At the back of the notebook, I note items that need to be purchased. Sometimes this might be larger items, like a new vacuum, or smaller items like paper towels. This list keeps me from buying things on impulse just because they appear to be a "good deal!" If I don't really need something, then it's not a good deal no matter what the cost!
I also keep a list on my computer of gifts that I've purchased. This list helps me from having a too-huge pile of gifts to wrap for the holidays, and it also helps me from realizing at the last minute that I've completely forgotten my FIL. This time of year, the list receives careful consideration almost daily, and helps me from spending too much.
Lists also help keep grocery costs under control. When I shop with a list (and a menu plan), I will buy less and avoid "hmmm, this looks like a good deal . . . " It also prevents me from bringing home another box of cereal when there are 6 in the cupboard already!
Lists are definitely a money saving tool in this household! The better my lists, the more in control I am of our budget.