What works for me to 'quiet my mind' is simply to repeat the alphabet mentally, at a moderately fast speed, continuously. Somehow this manages to 'block out' a great amount of my language-based thoughts, so that most of my thoughts are purely conceptual. These types of thoughts are much 'quieter', so you can fall asleep with them more easily. (and presumably this would work for meditation as well)

For example, when I first started trying repeating the alphabet mentally, and I wanted to remember what my three-step todo list was, at first I was only able to see the three parts conceptually, as icons next to each other signifying each task. To mentally voice my three-word 'mantra' would disrupt my mental alphabet repetition every time, presumably because the mental voicing of the letters took up the language processing part, so I couldn't combine them. Now I can, though, after practicing for quite a few hours.

Also, at first repeating the alphabet is difficult, but eventually it becomes very easy, almost subconscious. I've done it for many minutes, if not hours, straight, while doing other things and thinking about other things. (for instance right now--I'm testing it out as a lucid dream induction technique)