You don't have to go green "cold turkey." I personally hate wasting anything, so I have to use every last possible tiny little bit of toothpaste in the tube before throwing it away. The next time something in your home runs out or gets used up, see if there's a greener way to replace it.
Use rechargeable batteries the next time you buy new batteries.
When your light bulbs burn out, replace them with CFLs.
Make sure you turn off the lights when you leave the room.
Turn off the water when brushing your teeth, etc.
Take your own reusable bags to the grocery store, the mall, etc. There are so many fun ones out there. I have the ones from the grocery store that I use for food, and I have other ones for the mall, etc. You can get fun ones at The Disney Store, Babies R Us, and other places you shop regularly, and Kohls has some great ones that are extra big. Another great resource is ReusableBags.com: Better Bags for a Better Planet and More! A great idea is to use a reusable bag as a gift bag (again, check out The Disney Store for great kids' bags), and then the recipient also has a shopping bag. Not only are these bags better for the environment and all, but they hold way more than the typical grocery bag... which means fewer trips back and forth from the car when you get home from the grocery store!
If you get plastic bags at the grocery store, please recycle them. Use them as litter bags in the car, diaper bags in the nursery, or return them to the plastic bag recycling bins just inside most grocery stores. If you are local, we'll take them at our market, where we re-use people's bags from other places rather than buying plastic bags.
Remove yourself from junk mail lists at https://www.dmachoice.org/.
Pay your bills online instead of getting paper bills and mailing them in.
Instead of using paper for phone messages, get a white board and a dry erase marker and post them near you phone/in a central location (the kitchen?).
Reuse your scrap paper. Take messages or jot down notes on those return envelopes you never use, etc.
Use stainless steel travel mugs and water bottles instead of the styrofoam cups and plastic water bottles.
Use cloth napkins instead of buying paper ones... you can have lots of fun with this with colors, seasonal prints, etc. Buy each member of the family their own special napkin ring. If you sew, you can even make your own in any fabric you want.
Along the same lines, use hankies instead of tissues. They are gentler on those poor little noses getting wiped constantly in the winter, anyway. I just fold mine and keep them in a tissue box, so everyone still knows where to find them. And I keep tissues around for guests.
Challenge yourself to see how many fewer paper towels you can use. Next time you reach for a paper towel, grab a kitchen towel instead. You can just throw it in the wash when you are finished. :)