First, a surprising requirement:
Black Hair clippings have the odd property of being HIGHLY irritating to the skin. It's something to do with the angle they get cut at, and the texture. Those little clippings are sharp! And by the time the final cut is made, they will be *little* clippings. So, unless you enjoy TOTAL MISERY, take all your clothes off. Even your underwear! If you don't, the clippings will get into the clothes fibers and drive you mad! And they won't go away again until you've washed your clothes twice, either! It's much easier to prevent clothes-of-itchy-torture, by not wearing any, than it is to fix them later.
I've made the mistake of doing this with clothes on, and it's not something I'd repeat. You'll notice that all the pictures of me cutting my hair are cropped very close-up, to show only my head and maybe just a bit of my neck. There is a REASON for that...
If someone else is cutting your hair for you, you can use one of those plastic thingies to keep the clippings away from your clothes. But when you do your own, one of those would only bunch up as soon as you raised your arms, and then it'll do nothing for you.
And, of course, if you're cutting someone else's hair, give them a plastic thingy or a towel to put in their collar, and have them keep their clothes on! :-)
Now on to the actual cutting!
Run the clipper through the hair slowly! This helps to ensure that the hair will actually be cut, instead of just bending over. DO NOT HURRY! Hurrying is a great way to end up with a job that looks like you did it yourself. And you don't want anyone to be able to figure that out, unless you choose to tell them! You won't be able to see the benefit of taking your time until the final stages. But this is part of the foundation of getting a nice, even cut.
When you get to the front of your head, DO NOT turn around and go front to back! Start the next pass at the back again. At this point, all cutting should be done back-to-front. Overlap the cuts. The only way to describe it is, do the overlaps like mowing a lawn. Each row should overlap the one before it a little bit.
One other thing, DO NOT COMB the hair after completing this segment!!!
Just so there's no surprises,
Here's what it looks like at the halfway point of this phase:
Eek~!! You can see how one half is shorter than the other, but it's still pretty ragged.
And here's what it looks like when the "first pass" phase is complete:
As you can see, this haircut is NOT done yet! The first pass is definitely the "rough cut." But it's necessary. The clippers just can't bring it all down at once.