Step 1: Shorter - Term Changes
Reduce - Reuse - Recycle - This may sound like a no brainer, but alot of Americans throw perfectly reusable items into the can every year. One thing you might consider is using older electronics as storage devices or donating to the Salvation Army (which can get a tax deduction as well as help a person who needs it). You may also think about buying clothes made recycled material such as plastic.
Use CFL bulbs - They consume 75% less electricity than traditional bulbs.
Go on a "paper - less diet" - Reduce your use of paper by doing things digitally, such as creating your shopping-list on your cellphone.
Use low-flow water fixtures - It not only saves water but also saves you money on your water bill.
Use your bike - Stop polluting the earth with your car and ride a bike! It not only reduces your carbon footprint, but waistline too! (Walking is also recommended.)
Buy locally - Buying locally cuts the demand for commercial trucking to super markets, stimulates your local economy, and is a healthier choice.
Recharge! - Using products with rechargeable batteries greatly reduces the amount of disposable waste going into landfills.
Automate your thermostat - Replace your manual thermostat with an automated one. It can save you alot of money each year by turning off the A/C or heat when your asleep or out of the house. In addition to that, search around your house for cracks and a openings that let air and heat in and out of the house.
Control your computer - Use your computer's energy management utility to automatically put your computer in stand-by, hibernation, or sleep to save power.
Use a Smart Strip - It cuts off the power to each device as you turn it off to prevent the use of "idle power".
Step 2: Longer - Term Changes
Buy Energy Star appliances - Going to http://www.energystar.gov/ will give a list of Energy Star appliances.
Use solar panels - Using solar panels not only cuts your full dependency on the electricity coming from the power grid, it also provides you with a clean source of energy as well as government incentives. You might also consider the use of wind energy via wind turbines.
Buy a greener car - Next time your out shopping for another vehicle, choose a one that uses alternative sources of energy like electricity, solar, or even water.
Check your windows - Check out your windows to make sure that there is no heat loss during the winter. If you come to find that there is, consider replacing all windows in your home with double pan ones to prevent it from happening again.
Buy/ Build a house made from recyclable material - If your in or going to be in the market for a house, try going with one that's made from recycled material such as old shipping containers.
Get a laptop - Cut the cord by getting a laptop instead of a desktop computer. It uses less electricity and is able to be carried around so you can use it anywhere you like. I would advise the new Apple Macbook Pro, which is one the greenest laptops in production, keeps its value longer than alot of other laptops out on the market, uses Mac OS X Leopard (which virtually is virus-proof), and is durable thanks to it's aluminum uni-body case.