Make sure to save your cup sleeve from your favorite coffee shop and reuse it. They're usually made from recycled material, but reuse is always far more efficient than recycling. One sleeve should easily last months. There are also plenty of patterns out there that you can use to make your own reusable sleeve.
There are a number of sites that will help you remove your name from direct mail (i.e. junk mail) mailing lists. Register with them and save energy and resources being wasted on delivering to your mail box a bunch of crap you have no interest in.
It's time to replace those incandescent bulbs with CFLs, or compact fluorescent lights. CFLs use 75% less energy than incandescent bulbs, and can last up to 10 times longer. They don't buzz or flicker, and most turn on immediately. The color and quality of the light may take a few days to get used to, but the savings are worth it.
Turn off your car when you aren't moving. According to one source, "An idling engine produces 50 to 100 more emissions than a warm engine. Plus, cars get the worst gas mileage when idling cold or warm. Gas is being burned for no forward motion."
Go vegetarian! The process of producing meat for food contributes more greenhouse gases than all the cars and trucks in the world combined. Meat production adds pollution, methane, deforestation, and fuel consumption for transportation and petroleum-based fertilizers to grow feed. If you do eat meat, choose pasture-raised meat from a local farm.
Rather than putting magazines directly into the recycling bin, pass them on to another reader. Many places appreciate "recycled" magazines (medical centers, senior centers, etc.) or just share with a friend.
Planning to buy a new book, bike, or any other stuff? Try Craigslist, eBay, and Amazon for used books first. This reduces energy consumption for producing new goods.
If it's yellow, let it mellow. If it's brown, flush it down. OK, this one is pretty much self explanatory. If it starts to smell, flush it. A single toilet flush is anywhere from 1.6 to 5 gallons of water, and most of us flush the toilet at least 5 times a day.
Keep recycling containers or bags in different parts of the house. That way when you have a used-up toilet paper tube or empty shampoo bottle you will be more likely to recycle it than just throw it away.
Don't use screen savers. Turn your monitor off instead, or configure your computer to automatically turn it off when not in use. Screen savers may save pixels, but they waste energy. Turning your monitor off saves both pixels and energy.