Create a "Yellow Highlighter" style in InDesign.
Here's a light InDesign tip for any designers finding themselves cranking out the occasional old-school direct mail letter. You can easily create a "yellow highlighter" character style with InDesign's Custom Underline feature.
While the effect itself is a bit cheesy, the technique does let us demonstrate a few shortcuts using InDesign's character styles.
Step 1: Create a Custom Underline.
Let's use a few tricks to build this style quickly. First, select some type you wish to highlight, and Option-Click (Mac) or Alt-Click (Win) on the Underline icon in InDesign's Control palette.
Which brings up InDesign's Underline Options dialog.
Give your underline stroke a weight that is several points larger than your current type size, and use a negative offset to move the underline up to center around your type. You'll need to experiment a bit with these settings to get the look just right.
Step 2: Save it as a Character Style.
Once you've got your highlight effect tweaked properly, save it as a character style.
Option-Click (Mac) or Alt-Click (Win) on the New Character Style button in the Character Styles palette, then give it a name and click OK.
You may now highlight text to your heart's content.
Source: This topic partially inspired by this week's upcoming 90-minute mini-workshop in Seattle covering InDesign: Style Sheets. The actual tip comes from David Blatner on the always excellent InDesignSecrets blog.