Hmm ... with no important info, or clear objective stated, I would suggest this:
1) Read up on different diffusers and what conditions they are useful in
2) Find out about using direct diffused (diffused but no bounce) flash techniques and what accessories you need like small softbox attachment
3) Think if using simple direct flash might be better for you
4) Read the EOS flash bible and understand how mah fan Canon's flash system is. If you understand and master this, all the mystery of under or over-exposure with EX units will become clear.
Don't worry, it's only 45 pages long but contains more practical information than your instruction manual. :bsmilie:
http://photonotes.org/articles/eos-flash/
5) Google 'digital flash technique' and 'basic flash technique' or look up 'how to get the best out of the 430 EXII'. In-depth reviews usually give important insights on how a particular piece of equipment was designed/works, and it's shortfalls. Google 'EOS 430 EX II flash reviews'.
All the best.