I marked my frets out with a fine pencil line, checked it ,checked it once more , and another just in case, then put a tri square along the fret line and scored it with a Stanley knife (with a new blade in) when that is done you have a slot for your saw blade to sit into and saw away.
They came out very well. I was very pleased with it, my first build as well.
One other thing after I did all that checking I left the pencil marked board overnight and re checked it the next day, that way I thought if I was fatigued the previous day it should show up on the re check.
It's not as scarry as it seems