[Ki-Mono]

This is quite jumbled, so I'll probably upload a version without all the red-line as you can actually see the artwork lol.

Sorry for the wait. Drawing faces is a big struggle for me, so I was putting this off tbh ^-^;
I recommend looking at real face pictures for reference to get better at realism, since mine is not perfect. However, this is more to help with understanding what does where. So hopefully I did that much.

I'll work from top to bottom:

The forehead is about the length of your fingers (put your hand up to your face now and see what I mean). A general rule is the forehead, face, and mouth/chin, area have an equal amount of space. This isn't a perfect guideline, but it's something to work with.
Your hair-line is where your hair actually comes out from your head. So it should always be the source of where the hair comes from. From a front view, the hair with follow the head shape (just a little below), but more in a squarish shape. It will then have a bit of a "dip" or curve following the shape of the eyebrows.
Eyebrows a little over half an eye length above the eyes, and extend them by only just a smidge.

Eyes themselves are usually smaller then expected. This is probably due to the fact so many people are used to anime eyes. However, to get the actual sizing right, I recommend looking at real reference pictures. Otherwise, in general, I find it easiest to just start out drawing the face with the eyes first. That way you can just work the rest around it instead of fitting them in later.
Eyes are about an eye-length apart from one another, and a half eye-length away from the side of the head. They have an eyelid crease above, and a eye-bag line below.
The nose extends from the eyebrow area, dips inward at the eyes, and then extends outward as it goes down. Usually lining up nicely with closest edge of the eyes.
Ears appear at the upper part of the eye and end at the lower part of the nose. How far the extend outward is different from person to person.
The cheekbone is right under the eye, and can extend right around the place you drew the ear. It usually dips inward at the base of the nose.

Under the nose is usually some lip and smile lines. I sometimes find it hard to add these things without making the character appear too old, which is probably why they are left out of most anime and cartoon art styles. However, it's better to add them if you are going for realism. Lip lines are a simple "v" shape that lines up in between the lips. Smile lines extend from the nose, to a little outward from the mouth. It's more prominent based off the facial expression you are going for.
The middle of the mouth lines up with the middle of the face, and ends on either side around the middle of the eyes.
The thickness of lips and chin differ from person to person, so you will have to experiment with reference photos etc to get the feel of what you want.
Head shape usually extends around the mouth area, and dips in a bit before going out again for the chin.

Side notes:
The neck is around the thickness of the head and dips in slightly in the middle.
Hair is it's own thing, and doesn't lay completely flat against the head. All hair has a little floof and weight to it, unless it's really yucky and oily. Use soft and care-free strokes to sketch hair. You'll get used to it the more you do it.

And of course always remember every face is different! No face is usually totally perfect either, so having a face slightly "off" grid is okay! Looking up different races of people can help you get an idea of just how different a face can look while still following basic guidelines.
And of course it's fine to begin to develop your own style from these "rules". I personally took art classes that taught me how to draw realism, but I prefer to draw my eyes and ears big, with simple noses and mouths, and small necks. You'll find what you like and what you don't like as you draw.

Oof, forgot the references again: x x and just general pictures of faces on Google

[Leopard_14]

thank you so much! this is really helpful.