Just found another site that has some good info about Betfair, bet trading, etc. It is mainly of use to someone starting out and I reckon is mainly there to entice you to buy stuff, but information is information, so it may be worth a look.
Click here to have a look (BTW, I have no involvement, relationship or anything with this site, just thought it had some useful stuff on it)
"How to Stop Losing and Start Profiting"