Originally Posted by
Simon Barden
Use a straight edge and see how big a gap you've got between it and the first couple of frets,as that's how much the other frets will will need to come down; or at least the 3rd fret, with the others reducing in height reduction as you go up the neck. You want the tops of the frets level, but you can allow the fret height to vary (though this is not the ideal it is practical). In effect you want to draw a straight line between the first and last fret, and take the tops off the other frets until they reach that line, with the most coming off that 3rd fret. Easier said than done though without running up quite a complicated jig.