Hope you guys don't mind that I bring this thread back from the grave, but I made a REALLY simple tutorial of one of my ways to tackle a quick sketch, and I heard it helped a few guys, so I wanted to show it around here as well.
Nowadays I use this method both for sketching and to get a base to clean later for when I make a more complex drawing. I used SAI to make this, and I'm 100% this can be done on Photoshop, but besides those programs I'm not sure if those steps can be imitated on other drawing programs.
I'm also posting a video of a sped up process of a drawing of mine, which shows how I use this tutorial (just the first minute, the rest of it is me cleaning the messy sketch), one of my workflows when I'm drawing, and how much I rotate the canvas around.
[youtube]http://www.youtube.com/watch?v=eyK5PgXPqv4[/youtube]