Most of my work is heavily based on typography. I used to make 2D and 3D typographic illustrations by drawing letters on paper and then making vector graphics out of them, but recently I've been creating typographic illustrations in Google SketchUp Pro and then transferring them to Illustrator to finalise.
This method enables me to better show the letterforms' volume, make them more complex and choose the best perspective. Before using this technique I always drew letters in isometric projection.
The basic process of creating a 3D typographic illustration is simple: trace 2D letter outlines which you've sketched, make them 3D, put them together to form words, add a background and some additional elements, choose the best perspective, colour the illustration, and add some final details. I don't have space to describe all the SketchUp Pro tips and tricks in this tutorial, so if you're not familiar with it, you may find these video tutorials useful.