I'm not going to lie, I have a serious control issue when it comes to my hair, my hair is my thing and I have a hard time letting new hairdressers hack it up since I expect them to ruin my hair, and my hair doesn't grow back the fastest. Either I'm really picky or just unlucky, but I've rarely left a hairdresser super happy with my color and cut together. I'm still searching for a hairdresser that will really deliver, but In the meantime, I trim my hair once a month in a fool proof manner to make sure I at least get rid of the split ends (most of the time when I ask for a trim at the salon, I lose at least 5 inches which is crazy to me).
I have slight layers so this method maintains them. I use two different type of scissors, both of them specifically for hair cutting. One of them is to cut straight, and the other is for layering when I want to thin out a specific area for more subtle edges. I don't recommend this for everyone, but this method is hard to mess up unless you cut off too much, but it's great for a trim to ensure your constantly removing the split ends.