I will add two additional notes to this topic. The first one is about the number of segments, the second one is about hair-dynamics and animation.
In some videos, also in this one
https://www.blendernation.com/2017/09/19/blender-hair-tutorial/, people are pushing scalp faces deep into the skull, so that the emitted hair could follow the form of the head. The real problem is, that normally all segments have the same length, when you create them. And we do not want too many of them. So what we need are more segments near the skull and less far away. Here is a simple method how you can achieve this (Wolgade told me about subdividing the hair after creation, so this is the best way I can use it).
In the example I only took five segments and 4 strands to make it visible (the rest of the hair is hidden). You should do it with no hair hidden. So use point-mode for selection, select root, then NUMPAD CTRL +, do a subdivide, deselect element (select less, NUMPAD CTRL -) and repeat the procedure. Two segments more, exactly where we need them. You can do this, after you created the hair with a fixed number of segments as well without loosing all information of e.g. styling.
The second note is about animation and hair-dynamics I'm using in this video:
http://www.makehumancommunity.org/forum/download/file.php?id=5693It looks quite natural, but the hair is moving a bit like slow-motion. I can't change this for now, otherwise other problems will appear (see picture). In the beginning I was very skeptical about hair-dynamics. When you switch it on, and press the animation button, the hair simply disappears in the skull. But you can reduce weight (even to zero) and increase stiffness and damping. That is all I did. In the picture the values for my animation are presented followed by an example of less s´damping and stiffness and a low weight:
The complete motion was controlled with the previewer. Blender creates all the frames once (this takes some time and you will see your video in slow-motion). When the system has created the hair-dynamics, the video is played nearly in realtime. If you switch on AV-sync, you get the realtime result.
Additional hints: Switch off skeleton and eye-lashes in the previewer. To see the eyes instead of these white spheres in the preview I added a special mask-modifier to hide the transparent part. The modifier only works in the preview. This is sufficient for a preview, you also can see if it is synchronized to the sound (sorry video is only uploaded without sound for copyright reasons). Then render a few pictures, before you start to render the whole scene.