The SB900 type of flash is like a Swiss Knife, have everything that you will possibility need and make it easy for you. You can read through the manual and try to remember all the features and how to activate them, but utimately is still when will you need it. Suggest you read through those books or sites on Flash Photography. Think of what you need to achieve, then think back/refer to the manual of which Flash feature can help you on it in a short cut way, than to struggle with the Manual, and try to understand what each function can do for you.
There can be 1000 colours available to an artist, but which one to use, it all depend on what the artist want to draw.
Cheers!