There's an oring on the bottom, usually a new filter comes with it. There's also a drain valve that can also leak. Some folks like to delete all this, but bear in mind that when you do this you run the risk of passing water into your injectors pump and injectors.
Clean it up really good and see if you can see where it's weeping from. If it's the large oring on the bottom, it should be a pretty easy fix: go buy a new fuel filter (the one for the separate bottom water separator like the one that's on your truck) and you'll get the big o-ring. If it was me, I'd make sure I started and warmed up my truck. Removed the fuel filter, inspect and replace the big oring on the bottom, fill the fuel filter with clean ATF or diesel fuel (I like ATF as it comes in a handy bottle, it's easier to pour and store than fresh diesel, and it lubricates your injector pump) and fire up your truck. Remember, don't crank your truck for more than 10-15 seconds at a time after a filter change as you could damage your starter.
Good luck, and let us know where you find the leak.