It takes some study to get it firmly in your mind - but the all but one principle is pretty simple. You need to know three things.
All fouls are penalized from the basic spot - except for a foul by the offense behind the basic spot, which is enforced from the spot of the foul. See rule 10-5 for exceptions to the all but one principle.
Basic spot
The basic spot on a running play is the end of the run.
The basic spot of a loose ball play is the previous spot.
The basic spot on PSK is the spot where the kick ended (2-16-2g).
Page 74 of the rule book explains running play vs. loose ball play - read and study it. For me, that's requires the most study every year just to keep it fresh in my mind.
Go to my crew's website at
http://www.lakefield.net/~dday/ref.htm and send me an e-mail - I have a PowerPoint I can send to you.