When I choose a guitar I make sure that the harmonics line up with the fretted notes when tuning the guitar.
I also play some chords up the neck to see if they are still in tune an octave higher.
I like fairly low action myself but if you're going to be thrashing it then you may want it a bit higher.
If all this is good, the neck is straight and it's not cracked in the body then that's usually good enough for me.
Obviously you want to hear how it sounds and have a bit of a play but that's about it for me.
Head down to your local music centre and have a go on a few guitars.
You'll find one you like.