Wow - someone's not reading their Tips & Tricks! (see Issue 3, Dec '07, "Handy Tips for Everyone")
Very basic function everyone should know. Just go to the Layout menu, then select Snap, then type in the desired value in the Snap Interval box. You can also choose whether to Snap Objects to Grid, etc., etc.
I often change the grid sizes several times during the layout of a project. Really helps to put things exactly where you need them, quickly and easily. Try it, you'll like it!