I want to craft an exceptional boost to my Tower of Despair ring. How do I do that?
Try the DDO wiki page.
The DDO Wiki has a very nice section on DDOs crafting system. I suggest you go there and spend sometime going through the various sections. Each alter does different things and almost all of them are useful at different times in your characters development.
One place that provides a guide to crafting your rings is here: http://www.iro.umontreal.ca/~delallea/ddo/ring/cgi-bin/ring.cgi
This link lets you choose an exceptional boost for your ring, and tells you which ingredients you need and which sub-components you need to craft in order to create the final boosted ring.