Honestly, I learned most from Hunting Shows. I have been watching hunting shows for as long as I can remeber. They all have a tip clip in their show's, and they have helped me a ton!

A close second would be forums just like this one! There is so much information in these forums. And So many great people willing to lend a helping hand!

Oh by the way, gpi= Grains Per Inch. It is the scale at witch arrows are measured in weight. People generally use heavier arrows for hunting applications, and lighter arrows for target applications. Heavier arrow = more penetration!!

Good Luck! And keep reading!