If you have a front fringe, you'll know it gets long pretty quickly, way before you feel like going to the hairdressers to snip the rest of your hair. This is because a front fringe to your eyebrows doesn't have to grow very far to get annoying.
This method of cutting your fringe is flattering, cuz the hair line curves slowly upwards in the middle and feathers itself out a lot. so it never looks like it's just been cut (and it covers up a lot of mistakes), leaving room for error to only remain in how short you choose to cut it, rather than a mess-up in how you cut it.
Measure with fingers how much you want off.
Get all your fringe into your dominant hand. You may want to tie back the remainder of your hair to make this easier.
Lift it up at a 60 degree angle to the horizon. Go for a little more for more feathering, but stay away from pulling it straight up.
Twist until it's good and twisted.
hold your hair by the very end and snip off how much you wanted in a straight line across the twisted mass.
discard hair and check fringe length for satisfaction.