Saving water is incredibly easy. Just do it.

As an avid container gardener, I use a lot of water on my many plants. 32 plants to be exact. I would use about 10 gallons every couple of days. I finally got around to putting a bucket in my shower to catch the "warm up" water. When it's full I water my plants with it. I now don't have to turn a faucet on to water my plants.

Bonus green points: the bucket is actually a refillable cat litter package that we don't use for cat litter anymore, reused.

Even if you don't have plants, you can use it to flush the toilet (just pour it in the bowl and it'll flush). There's simply NO reason not to do this. It couldn't be easier. Just do it.