As a professional hairstylist, I often get asked about trimming your bangs at home. My short answer is always, “Don’t.” But my long answer is, “Okay, if you absolutely MUST trim your bangs at home, here are the things you have to do..."
Get hair-cutting scissors. DO NOT CUT YOUR BANGS WITH KITCHEN SCISSORS.
I will repeat that in case you weren’t listening the first time. DO NOT CUT YOUR BANGS WITH KITCHEN SCISSORS. You can get some good scissors for about 20 dollars at Sally Beauty or Ulta. If you’re trimming your bangs at home, this is worth the investment. Also, buy a comb! Don’t try and just use a brush or whatever you have lying around. A regular comb.
Cut your bangs when they are clean and dry.
Always cut into your bangs vertically, never horizontally. You want to take little bites with the scissors and work your way across. I like to use my comb to hold the hair without any tension. Again, never cut horizontally; this is the fastest way to end up with super short, crooked bangs.
Remember, it's always best to use your favorite pro hairstylist. But in a pinch and with some practice, you can have success giving your own bangs a trim at home now and again. Good luck!