Trumpy, here is a very basic site that explains what happens, but like I said, very basic, it's atcually done for kids to understand. http://skydiary.com/kids/lightning.html
Alot more goes into how, why and where lightning will strike. Stuff like ions,isokeraunic levels, inductance, ect..
Roger Block's book is awesome on this, if you have the time to read over and over again. It's kinda confusing.
