The best way I ever cheated on a test was to take the white lining out of a candy bar, write on it, and stick it back in the wrapper on my desk. I'm glad I didn't need to cheat in college though, and was able to make through on my own knowledge.
As a TA now for engineering classes, I'm astonished by the amount of cheating that goes on. It's unreal and I can't believe how bad people are at it. Students will go online and purchase the solution manual to a textbook and then copy the solutions word for word on their homework. When you grade homework this is so easy to spot. Also, and this really amazes me, students will get like 3-4 old copies of a professors test given over the years and completely memorize the problems. Professors in our department don't change their tests that much from year to year, but they need to.