What is the best method of scrambling a rubik's cube?

If I wanted to solve a physical Rubik's cube multiple times, for practice, what is the best, most random way, to scramble the solved cube?

The best way I can think is to hold it behind my back and turn randomly until, when I look at it, it looks random enough.

Is there a better way?

Answer

If you're willing to take the time: The World Cube Association has a specific method for shuffling their cubes. They use a program called TNoodle to do the scrambling; the program generates a "scramble sequence" which can be followed to produce a scrambled cube.

Their code actually features a nice interface to generate the scrambles:

I have yet to figure out what the "Adjust Events" options do, but producing the scramble sequences just comes down to clicking the "Scramble!" button.

Here's the result of running their program:

There is also an online interface here. I used it to scramble my new 30x30x30 Rubik's cube: