Center that Guide

If you drag a guide from the ruler onto the page and you want to make sure it’s centered horizontally or vertically, try this: Press Command Option-; to unlock the guides. If necessary make sure that only one guide is selected by deselecting every guide and then clicking on the guide you want centered.

Then in the align palette (Window>Align), use that flyout menu to select Align to Artboard. Click on the Vertical Align Center icon (or Horizontal Align Center icon, depending on the direction of the guide).

Quick Delete From Palettes

To delete items from a palette without getting a dialog asking you to confirm your choice, hold down Option as you click on the palette’s trash icon. This applies to brushes, swatches, actions, etc. You can also click-and-drag an item to the trash icon without getting a warning.

Multiple Tools?

If you’re really efficient (lazy?) you can tear off multiples of the same tool menu and position them all over the screen. This way if you have a large monitor, you can always have Type tool nearby without moving too far.

Measure From Where You Want

By default, the rulers display with the top left of the page set to zero for the horizontal ruler, while the vertical ruler displays zero at the bottom left of the page. To change the ruler origins, click on the top-left corner of the rulers and drag to wherever you want to set zero.

Actual Size, Fit in Window

In Illustrator, there is often more than one way to do things, and zooming in and out is no different. You can use keyboard shortcuts to change the view to Actual Size (Command-1) and Fit in Window (Command-Zero) you can also change to these views using the Toolbox. Double-click on the Zoom tool to change to Actual Size view; double-click on the Hand tool to change to Fit in Window.