How can I change the leading in a field that uses HTML field scripting?

Leading (vertical line spacing) is usually controlled in a field's Format tab. If you would like to have text with different leadings inside a single field, you will also use the Field Scripting tab.

To change the vertical line spacing, use the following HTML script:

<stylerun linespacing=n> where "n" is the number of additional points of leading beyond what is set in the field's Format tab.
(Note: If "Auto" is selected from the Leading menu in the Format tab, the leading will be the same as whatever the current font size is.)

linespacing=0 means no additional leading beyond the font's normal spacing.
linespacing=n adds n points of leading.
linespacing=-n tightens up the lines.

So, if the font size is 8 pt, and you use <stylerun linespacing=3> then the leading will be set to 11 pt.
 
Example:
You need your text to look like this
Name
Title
Title 2
 
Notice that the space between the name and title 1 is greater than the space between the two title lines.  The name is in an 18 point font and the titles are in 14 point font. To set this up, you would set your font size on the Format tab of the field containing your field script to 14.  Your script would look like this:
<font size="14">@Name@</font> <br/> <stylerun linespacing=-7><br/></stylerun> @Title@ <br/> @Title2@
 
Notice that there is a linebreak surronded by the stylerun tags using linespacing to adjst the space between Name and Title to be 7 points.  A negative number is being used to reduce the 14 point line size by 7 points.