Here's the quick way to check your nut for string height at the nut in relation to your first and second frets. It's a quickway to tell if your frets are worn and/or if your nut is worn. The photos show a few steps to take when measuring what the string height on a new nut should be.
Flatten a pencil at least as long to extend the length of two frets.
This photo shows marking a new nut but you can make a small mark on your nut (after removing string(s) to show you where you're at.
Here's a pic of how your string(s) should be sitting in the nut slot and the red mark is where the pencil should hit on your nut:
Naturally there's a lot more involved with a setup but these are quick checks so you'll know where you stand as far as your 1st fret (F) on your E string. This also works on all your strings, but you can just loosen your E string enough to move it out of the way to run the flattened pencil holding it flat against the first two frets.
This info was snagged from here:
Making a New Bone Nut
http://www.frets.com/FRETSPAGES/Luth...t/newnut1.html