I'm constantly surprised by how few people are aware of the following feature. It runs throughout the entire Creative Suite, be it Photoshop, Illustrator, etc.. If you don't already know it, this tip will radically change the way that you work.

Simply ensure that your cursor is in any field in any dialogue box or palette (panel in CS3) and use the up and down arrows to intuitively change the value of the field. For example, place your cursor in the font size field of Illustrator and the font size will go up or down in 1pt increments. Alternatively, place your cursor in the rotate field of InDesign and the selected object will rotate in 1º increments.

It's a really good way of working. And once you're used to it, this will become second-nature to you.

NB If you want to go up or down in x10 increments simply hold down the shift key as you use the up and down arrows.