Camera manufactures like Canon seem to have new camera models every few months. As we grow into our hobbies, there are times where we may outgrow our cameras and need to upgrade, or maybe purchase a new camera. If selling off your old camera is part of your plan to afford something else, there's a few tricks i've learned to keep your resale value up. First, keep the boxes, software, and manuals. You might think this isn't important stuff because you're a seasoned veteran, but the next guy who wants your gently used camera, will find it handy. It also shows that you really care enough about your gear to keep these things in OEM condition.
Most important thing i've learned? Camera bodies will have scuff, scratches, and wear marks. Most people are fine with that. The one thing that can really make or break a sale are LCD screens. They might function perfectly, but if there's a slight scratch on it, the buying market might look for other options. The first thing I always do is purchase some of those Generic screen protectors used mainly on Mobile devices like iPhones and stuff. I cover the top LCD and the back LCD to prevent any scratches. When it's time to sell a camera, pull off the screen protector, and you'll get better response from a buyer if the LCD looks completely un-scratched. Available for pretty much any camera model you can think of, you'll find these products through the links below.
You can find them for sale as low as $0.01 + Free shipping, found here. You'll need to cut a little to get that perfect fit. No, that's not a Typo. I've actually won several auctions for 0.01 Cents (1 penny) + free shipping. It's most likely coming from overseas, so you'll need to be patient though. Hey you can't complain for 1 penny.
If you're willing to dish out $5.00 - $15.00 dollars, you can get the fancy Glass LCD screen protectors which is much more durable than a sheet of plastic, found here. Hey this one even says 550D on it, perfect for that T2i!