Magic lantern is by far the best thing to happen to the DSLR cameras. It offers so many options not given to you by the normal Canon firmware that it should be sin not to install it. This is a quick little walkthrough on how I use ML for easy, accurate free-lensing.
Now, if you don't know what free lensing is to start off with, basically its the poor mans tilt-shift. It requires you to detach your lens from the camera body holding it out and tilting it up or down, left or right to achieve the Tilt-shift look. (DISCLAIMER-I am not responsible if you drop your lens. Do this at your own risk) I have yet to drop a lens doing this, but it can happen very easily. Here is a quick tutorial on free lensing by Connor Surdi Photography.
Now, the next thing you need is Magic Lantern. You will need to go read through this site, download the files and install it to your camera before you can get the focus peaking to work. Its a very quick and simple "Hack". (Also not responsible if this messes up your camera) I have not had any issues and I have been using it since I got my first t2i. Very stable shell.
Finally, once you have Magic Lantern installed on your camera, press the delete button to access the ML menu. Go over to the overlay tab, find the "Focus Peak" option and press the set button on your camera to activate it. Switch to LV mode and you should see the little red focus dots appear on your screen. If for some reason they don't show up, when you're in LV, press the info button on your camera (Im using a 5D mark ii) until the dots appear.
That's about it for that! Works extremely well and have yet to miss focus on a free-lensed shot!