http://www.emblibrary.com/EL/ProjectInstructions.aspx

Here is a great place to start.

besure and put thin wws on top of the towel so the stitches don't sink down in .This trick just emproves the look hugs ,oh yes there are lots of freebees to try with on here and other sites ok carolyn

Excellent gift - embossed towels - also love to make them by dozens! Check the sister site Cute Alphabets for beautiful designs too!

Does personalise mean you want to digitise these designs yourself? In that case there's an excellent tutorial on Clipartopolis. It uses PE-design, but it can be done in more or less the same way in any digitising software.
There are lots of embossed alphabets available - here as well as on CuteAlphabets - which don't need personalising or you could go for a simple shield on which to embroider a name of your choice.