+1 on the fuel pump relay. If you don't hear the pump click when someone turns the key, I'd check there first. As others stated...usually if a filter clogs or a pump goes bad, you have some rough idling and poor acceleration beforehand as a warning sign.
If you don't get a click, figure out where the relay is and see if there are any relays for headlights/turn signals, etc that are the same size. Swap the relays and see if the pump turns on after that...if so, then you've found your problem.
Another possibility for you, being that my car had the same symptoms recently, is a bad camshaft position sensor. I went through all the diagnostic steps above and found no issues, but the car just wouldn't start some days. Finally the check engine light came on and the car threw the code for the camshaft sensor. It's typically a cheap/easy fix and another thing to consider with your truck suddenly not starting...my car was running fine, then *poof* just wouldn't start sometimes when I went to turn the key.