Knowing the diatonic chords in the key can help especially with tunes like Shadoogie where the progression is quite simple and as Justin says, intuitive to ears used to listening to pop and blues etc. A bit of theory here:
http://www.musictheory.net/lessons/43It becomes more challenging with more complex progressions and tunes that don't resolve so predictably (Sweet Dreams comes to mind). Memory is a complex thing. It's been said by experts that perfecting something can take 10,000 repetitions! So I think practice is the key along with developing some specific strategies for remembering the progressions (eg visualizing fingerboard positions and shapes, listening for clues from other instruments, learning 4 bars at a time, etc).
Right then. I'm off to learn the chords to the Warlord now ... 10.000 reps
