[Beladona]

1) your best teacher is to take an existing addon and use it as a reference. Something simple is best, and learning to change things like text strings and various other code is a really good way to start

2) if you have already learned to program using other languages, you have a head start. Learning Lua is very easy compared to most other, more strict, languages

3) wowwiki.com is your friend. Visit the Global API and Widget sections to get ideas on what you can do in Lua in WOW.

4) Understanding XML is VERY helpful, although not absolutely necessary for most projects

5) Last but not least. Do not hesitate to ask questions. There are peoplearound willing to help that have been doing this fro day one. Myself, Clad, and Iriel will always be looking around the forums for ways to assist people, so ask and we will try to help, time allowing.