Well, say you wanted a picture to be a third of the original. Divide the height by 3, you have your new height. Same with the width. The proportion isn't really necessary, I just like doing it that way. xD It's pretty easy. And photoshop kinda does the math for me. >>
It was sitting out in the cold muddy rain and it was starved. D= I fed it, cleaned it, and let it sleep in our bathroom.