First of all, turning things off really makes a difference. Just use a little common sense. For example, if you are walking out of a room for five minutes, don't bother. Like was indicated earlier, the difference minimal. If you are leaving a room for 15 minutes or more, then turn things off.
Finding ways to reduce the use of appliances help has well. I like the post about reading rather than watching TV or surfing the web. If possible, trade books with friends when you see them or borrow them from the library. It may save you more on the electric bill but it will keep money in your pocket by not spending it on books. Between reading and exercising outside, I haven't turned on my TV in a couple weeks.
I do use my home PC daily. However, I am only on long enough to answer necessary emails and when I am done with it, I shut down since it will use more energy during the hours it is idling than what it would use to boot it back up the next day. The link below is from Umbra Fisk of Grist.org answering a similar PC-related question.
Generally, a little common sense will go a long way. I set the heat/air conditioning back when I leave the house in the morning (everything in the house is electric), do only full loads of laundry (run the dryer as little as possible...about 75% of my laundry is dried on drying racks), take short showers (so the hot water heater works less), unplug small appliances when not in use (phantom usage...some pull power even when off...so unplug it or turn off the power strip), etc.
Not only will you use less energy, you will save money as well.