How can I identify quality bacon?
Just look out for artificial flavorings; a lot of bacon comes with artificial "hickory" or "maple" flavors, which are disgusting and often taste like chemicals.  The better bacon won't include such things.  Nitrate-free bacon is important if you're sensitive to nitrates.  The fat content is more of a matter of taste than a hard-and-fast rule; personally, I like a fair amount of fat because I like to cook other things in the rendered fat!  Same for the thickness.  If you like very crispy bacon, you may want your bacon slightly thinner than the "thick-cut" styles that command a price premium.