I use a utility knife rather than an exacto knife because you can use a little more force since grip tape is not the easiest thing to cut through. If you are cutting an straight line, cut against a metal ruler. Change your blade when it gets dull. Razor blades are cheap and this will make your life a lot easier. Also remember knifes are sharp and they will cut you if you are not paying attention to what you are doing. Get creative and have fun with it!