Fret the low E string at the first and 13th frets. There should be a bit of play at the 6-7 fret, maybe enough to slip a business card under.If there's too much, tighten the truss rod a bit, if not enough loosen it. A quarter to a half turn at a time then recheck. There should be about 3/32" clearance between the bottom of the low E string and the top of the 12th fret.

Sandy