How'd you know I wasn't already?

It's incredibly simple to understand, but very difficult to do. You need to practice spending time where you don't think. You want to empty your mind. This is obviously near impossible, you will have thoughts enter. The idea is to accept those thoughts, not beat yourself up about it, and simply categorize them as what they are and place them in the back of your mind to deal with later. Then return yourself to a not-thinking state.

I'm assuming it needs to be alone and completely quiet?

Just a guess.

You're female, but you almost seem to have a brain.

:p

Good guess. I'm a brunette. :)

Thought you were leaving. Can't sleep?

From what little I saw of Croyle (part of one game, and highlights), he has a strong arm and guts, both characteristics that Greise is lacking.

When you're starting, it will help to be alone. It will probably help to have some music that is very calm and quiet (classical, etc). Use the same music every time. You want to get into a routine of "I hear this music, I clear my mind, I become peaceful."

The next step is to control your breathing. Breathe very, very, deep. Breathe very, very slowly. One way to keep your mind clear is to count breathes. After you get to a certain point, stop counting them and start simply mentally tracking "in, out, in, out". At a certain point you can stop with that thinking.

You know, I've never practiced meditation, but I've never had any problem clearing my mind of thought and tuning out the distractions
around me.

How long did you have to practice?