Data Extraction

Hi BI Gurus,

I have recently come into the field of BW and i want to learn it, please tell me the way through which i can gain knowledge and right now i want to know about the various steps that are invovled at both of the ends in R/3 as well as BW for extraction ( Fulll & Delta) what settings we have to make or what step has to be done first and all. Is there anyone can guide me. Please tell me also the difference between the LO extraaction , Generic or any other type.

Guidence will be appreciated.