If you run some sort of activity that uses tickets (a carousel, for instance), consider switching from tickets to reusable tokens. My kids frequent a carousel where tickets are torn off and tossed in the trash moments later all day, every day. Hugely wasteful.
When looking for a housecleaning service, find one that uses earth-friendly, biodedgradable products. Or, alternatively, you can supply your own products.
For most recipes, preheating the oven isn't actually necessary and uses up more electricity or gas. Turn the oven on when you are ready to put your food in, and you can conserve more electricity gas.
Use biodegradable sponges. You might not think of sponges as having an impact, but think of how many we use in a lifetime. Every place you can make a change will have an impact.
Take your miniature shampoo and conditioner bottles home with you from hotel rooms. They must just get thrown away for safety reasons, so you might as well use them, and recycle the bottles when they're empty.
Computers consume much power. Turn off every machine every night if it is not needed. This will save a lot energy.
Put a recycling bin on every floor of your house. You're less likely to throw away paper and junk mail if you always have a recycling bin somewhat handy.
Resist the temptation of convenient squeeze bottles for things like mayonnaise and relish. You always end up throwing away a few servings because it's so hard to get the last of it out. Opt for good old fashioned (reusable) glass jars instead. No nation is so wealthy that it should regularly throw away food for the sake of convenience.
Do you put pudding or Jello packs in your kids' lunches? Prevent some waste by making your own snack-packs with reusable 1/2 cup containers (like Gladware) and any flavor of Jello or pudding they like. It only takes a few minutes to prepare the mix. Not to mention you'd save a bundle. Just remember to remind the kids to bring home the containers.
"The best time to plant a tree is 20 years ago. The second-best time is now." -African Proverb