Here's a cool little tip I stumbled across and was surprised I wasn't aware of it.

Illustrator dialog boxes will perform math functions. What this means is you can use math to create measurements you are uncertain of.

For example, you have an object you want to rotate around a center point. You want the object to rotate by a specific divisor of 360° -- say you want to split a circle (360°) into 15 equal parts and you want to rotate an object into each of these parts.

Draw the first object and select the Rotate Tool. Option-click (PC:Alt-click) the point you wish to rotate around. The rotate dialog box will appear. In the text field enter 360/15 -- 360° divided by 15 parts. Then click the "Copy" button. (See the top image below.)

This will place a second item (the copy) rotated the amount necessary to fit 15 objects around the center rotation point. (See the middle image below)

Now, it's a simple matter to choose Object > Transform > Transform Again (Mac: Command-d, PC: Ctrl-d) to repeat the rotate and copy 14 more times and you end up with exactly 15 items around a circle. (See bottom image below.)

This makes it possible to let Illustrator do the math for you rather than trying to figure out exactly how many degrees you need to rotate (or move) something to fit a space equally.

I don't know why it never occurred to me to use math in dialog fields before, but it's certainly a helpful tip.