At the grocery store

Buy 2 Liter Soda bottles, not cans.
Buy items in bulk when you can
Try not to buy individually wrapped snacks. (use those “re-used” zip locs if you must)
Re-use your paper grocery bags (use them double bagged, they’ll last longer)
Choose items that were packaged/made as close to your home as possible

Electricity and Water

Turn off as many appliances as you can when not in use – Computers, Monitors, Printers, Fax machines, Stereos, etc. They still draw a small amount of power, even when not running
Run dishwasher and laundry over-night when power rates are cheaper (hence less users)

Wash and Re-use your ziploc bags
Make a habit of carrying a tote bag every time you leave the house (in case you buy anything while out)
Leave a tote in your car; leave re-usable grocery bags in your car
Don’t buy bottled water – use your Nalgene!
A LOT of things can be recycled and it adds up: toilet paper rolls, asprin bottle boxes, junk mail, flyers
Start saving 8×10 sheets of paper that have a clean side, and make notepads
Rely less on paper towels (your kitchen towels can be used for more than drying your hands!)
Buy local!