This tip from Michael Viscetto is for old-school AutoCAD users.
In regard to editing dimension text, I am in the habit of going to the Properties dialog box and editing the Text Override area to obtain my custom text features, such as using "<>X"add text here"" to get my dims above and some text below the line. However it is now possible to just double-click the dimension and edit the text as if it were multiline text. Of course, this was pointed out to me by a much younger AutoCAD user.
Notes from Cadalyst tip reviewer R.K. McSwain: AutoCAD has been around for a long time — and so have some of us users. One thing I see on a frequent basis is new users picking up little tricks like this one, when in reality it is not even a trick. A recent version of AutoCAD made TEXTEDIT the standard command when you double-click a dimension, so new users just learn things like this automatically; they've never known another way.
Besides the dimension edit tip, another lesson to be learned from this is to listen to those newbies — you just might learn something.
If you are on an older version of AutoCAD, see CAD Tip #3901 for an way to configure your double-click options.