If you have to be away from home for an extended period of time and you have a lot of hanging baskets and/or container plants, put them all in a child's swimming pool or other large container.
In times of severe drought, re-route your washer hose to empty wash water into a barrel or large container. Every little bit helps!
When your work boots or tennis shoes wear out and are ready to discard, first remove the shoe strings for use in tying up tall flowers or veggie plants.
If your new transplants are getting too much sun, you can put an umbrella over them. Anchor the umbrella handle with something heavy like a concrete block, or drive a stake into the ground and tie the handle to it. You can also pound a length of pvc or galvanized pipe into the ground and drop the handle in.
If you have leftover coffee in your coffee pot, once it's cooled, you can water your plants with it. Do not use cream or sugar though. I have no scientific evidence to back this one up but I have a house plant that is 14 years old that gets the coffee remains and it is so healthy.