What little things do you do that save you lots of money?

Mine is always doing two transactions at places that give me coupons.

I had a coupon for $10 off any beauty item at CVS so I got a $10 eyeliner, and then $20 worth of other things that I needed, but I ran the eyeliner in a different transaction. They gave me coupons with the receipt for that, and I used two of them on the second transaction which ended up to $10 of savings, and only ended up spending $10 on $30 worth of stuff :D

So reddit what do you do that takes no time at all but saves you heaps of money?