I have a list of larger purchases I'm on the lookout for over the next X months (a powertap hub, a new tent, a replacement commuter bike - that sized stuff). If I manage to get it for cheap in various sales (e.g. Black Friday, Boxing Day, etc) then all the better, but I don't go out looking for things that aren't already on my list.
Any money I've save gets donated to charity, so it's a roundabout way of making large corporations donate to charity (I benefit by getting some extra gift aid tax relief too).