Disclaimer: The technique below on how to cut your own hair may not work for your hair type. If you are under 18 please only do it if you have parental/guardian consent. It works on my hair because my hair is unusually easy to work with.
My hair is a freak. It is straight-ish with a slight wave, thick and heavy. It does not curl no matter how hard I try (it might curl with a perm, but no amount of plaiting will make it hold a curl for longer than about half an hour). My bed hair looks like the sort of hair that has been through a straightener. It's so easy to manage that I don't have to really try hard to make it work. I am in no way trying to brag - this is just so you know why this cutting technique works for me as it may not work for you. Do not try it if you can't get it fixed up by a qualified hairdresser if it goes wrong. I take no responsibility for what you do to your own hair.
Read through ALL instructions BEFORE attempting this.
Tie up your hair. This is not as easy as it sounds. You hair will need to be tangle-free. Have the ties on your wrist, ready to go. Take the comb too. Bend right over forward so your head is upside-down. Now, comb your hair again while upside-down to check it's tangle-free and all hanging down evenly.
Gather your hair and tie it as close to your forehead as possible BUT gather it to the centre of where you always part it.
My hair parts naturally to the side, that's why the tie is off-centre in the pic. If your part is further off-centre than this, I do not recommend you cut your hair this way as it could look too un-even in the front: go to your usual hair-dresser and don't risk doing this yourself.
When you gather it, comb it so the hair is all going straight to the tie - you don't want any bobbly bits like I do in this pic (to the right side of the tie). The left side of the tie is how you want your hair to look. I'm soo not hot in this pic.
Tie your hair again. About 15cm further out from this tie. You may need to hang upside down again for this one so that it is coming straight out from your other tie. See pic below. I am soo not hot in this pic either. :)
Approach your scissors with confidence and, about 5cm away from the 2nd tie, about where the edge of my thumb is in the 'step 2 pic', cut. Cut it straight across, lop it right through. Off. Do not cut in between the ties - you will definitely cut it too short around your fringe/bangs. Your scissors should NOT be standard kitchen or paper-cutting scissors! Use hair-cutting scissors or fabric scissors. It will not ruin your fabric scissors. Your hair should be dry and clean. Any hair-stylist might squirm at the thought of fabric scissors so perhaps use hair-scissors. Sharp ones. See pic below. The toothpaste is there to give you perspective of how much I cut off. Yay.
Untie your hair, comb it, and ...... voila!
My hair is still really long, my fringe/bangs are about cheek-length. The back looks tidy and like it's done by a pro. Go on, it was done by a pro - me!