Cutting sponges in half. It just makes them harder to use, and then already last a long time and cost like $1 each. I'm not going out of my way to save ~$1/month.

Unplugging electronics. I have a kill-a-watt meter and did some math. It took more power for my computer to run the spreadsheet than I'd save by unplugging everything in my house. Electronics have gotten way better at managing phantom power draw.

And I'll second coupons. The only coupons I look at is the monthly Costco mailer, and I only really look at things I'll buy in bulk. I try to buy enough to last until the next sale, which has worked out pretty well so far. But I literally don't look at any other grocery store coupons because I just don't find much value there.

In fact, most of these frugal "tricks" are worthless. Just focus on the high value lifestyle choices (cooking at home instead of prepared meals, learning to DIY common repairs, etc), and ignore most of penny pinching. In other words, don't be penny wise and pound foolish.

That said, here are a couple of things that I do think are worthwhile even if the money savings isn't huge:

• cut my own hair - takes 15-20 min once a month, which is less time than I'd spend getting to and from the barber; it's essentially free ($20-30 for clippers, which I've used for dozens of hair cuts), but $20/month saved isn't why I do it, I just hate going to the barber, it just seems to take so much time
• change my car's oil - same as hair, it takes ~30 min, and most of that time I'm just sitting inside waiting for oil to drain; I don't save much money, but I do feel like I save time vs driving to/from the oil change place, and I use high equality OEM filters