This is what helped me back in the day when I did that stuff. I didn't know my ass from a hole in the ground and Avi's guides got me up and running, fully multi-homed!

http://freedman.net/bgbgp.ppt

http://freedman.net/bgp102.ppt

http://freedman.net/multi.ppt

http://avi.freedman.net/fromnetaxs/multi.html

http://avi.freedman.net/fromnetaxs/bgp/bgp.html

http://freedman.net/choose.ppt

First learn the basics of IP networking, looking for CCNA certification materials or Comptia Network+ materials would give you a good base of knowledge.

BGP is just the way networks exchange routes (paths to a specific IP address) between each other. Once you know a little bit about how routing works it will make sense.

BGP itself is fairly simple to understand and entirely disconnected from day to day networking, you could start on it with very minimal understanding of anything else.