Bit of a tutorial on facial features, not necessarily anime. Mostly portraying emotions.
So. For drawing faces, two of the most important elements in terms of emotions are the eyes and eyebrows. The eyes and eyebrows give away the emotion more than anything else. Starting with eyes, the eye shape will change depending on the style. In anime, because the pupil and iris move and change so much, the eye itself doesnt do much more than blink in terms of moving. The more realistic you get, the shape changes depending on emotion and facial movement. If someone if smiling a lot, their cheeks will make the eye curve because it is slightly close due to the cheek moving up, but the eye is fairly open still. For sadder, balling faces, the eye curves and is more closed than happier emotions or angrier. For shading, that actually changes too. Take for example, in gachas, if a character is emotionless or really sad, the highlight in their eye is gone usually. In real life, if someone has a similar emotional state to that, their eyes close a little more, which usually covers up light reflections, since most lighting comes from up. So for sadder emotions or emotionless eyes, dont draw a highlight or as much of one. For tears, happy or sad, have it well up near the eye in a little blob for tears not yet fallen, then draw a line that follows the face (curve it to go along the cheek instead of straight down) and then draw a tear droplet, and you can erase most of the lin that connect it to the eye, but leave a bit of a line connected to the droplet to see the path it took. For eyebrows, the more frustration, the more the eyebrows knit together in the center of the face, meanwhile the more carefree, the more the eyebrows seperate. A happy character will have eyebrows relatively wide apart (as normal as possible tho), and a very happy one might have the eyebrows turned up in the center. A sad character will have eyebrows close together, and the closer, the more sad and frustrated. Be sure to have a couple lines where the skin wrinkles from the closeness. For mouths, in a happy expression, draw a smile, the wider and taller, the happier, don't overdue it to the point it looks like the joker tho. In a sad expression, it doesn't matter much, unless it is a tragic and sad expression, then you would have crying and balling, and the mouth would be in kind of a sideways hourglass shape, since the mouth would likely be open then, and the part of the lip connected to the gums would not move much, causeing a kind of dip, while the rest of the mouth is wide open. Don't be afraid to draw wrinkles for facial expressions, it enhances the emotion, and doesn't make your character look old unless you use like 200 of them. For a neutral mouth expression, instead of drawing a straight line, try a slightly curved down one. The reason is, it is incredibly difficult to actually form a perfect straight line with your mouth, a curved down one is more natural. Now, with these tips, try drawing something like drama masks, or comedy and tragedy masks. They are really good to practise facial emotion, and you can do them in any style, though i recommend realistic ones.