Part your hair as you normally wear it.
Run a fine-tooth comb through your hair to get rid of any knots. You need completely tangle-free hair before starting, so the hairs are all cut in the right way. You don't want to end up with a sloppy cut, with stray hairs all over the place once you style your hair.
Section your hair so half lies at the front and half at the back.
Twist the front section of hair together and clip it up, out of the way.
Pull the back hair together into a ponytail at the back of your head. Holding the hair with your hands, twist it clockwise about 180 degrees so you've got a single twist in your hair.
Now it's time to make your cut. Don't worry, you can't mess up if you use the horizontal line technique, which is super easy and allows you cut the hair so it flows naturally. Cut across the hair in a horizontal line; the higher you cut, the shorter the hair at the back of your head will be.
Once you've cut all the way across the hair, let go of your hair and take a look. You'll see the hair is higher at the nape of your neck, then falls longer at the sides, creating a lovely bob. You can leave it as is, trim up the hair at the front to even it out, or use a pair of clippers to trim over the hair at the nape of your neck to get a more cropped 'do.
If you don't have a fine-tooth comb handy, you can use a brush, but the closely spaced teeth on the comb work better to get rid of tiny tangles, so you get the most polished, professional cut.
Make sure your scissors are sharp before starting the cut, otherwise you'll end up with a sloppy, uneven cut.
When you're sectioning your hair, picture an imaginary line across the top of your head, from the top of one ear over the crown of your head to the top of your other ear. This is where the section line should be, with half at the front and half at the back.
Remember, it's always better to have to make a few cuts and keep your hair the length you want, instead of accidentally taking off too much at one time, because you won't be able to snap your fingers and have your hair grow back.