What could the problem possibly be. Ran fine until yesterday morning when it wouldnt start. Battery is fine. Fuel pump was just put in a few months ago. When the key is turned, it turns over good, but backfires if thats any indication of a problem or not, I dont know. Where should I start with trying to diagnose this problem?

Its a 6-cyl
1997 S-10

How many miles on it and when was last tune up?
If no start check for lose of fuel pressure or good hot blue spark to all plugs.

What brand of fuel pump was installed in it?

I had a similar problem, spun over fine but would kinda spit or cough
(not really a backfire) it wound up bein the distributor cap & rotor.
it was mostly on a wet day,not all the time. The cap was green inside (moisture)