It looks like no one ever gave you tips on hair, so here it goes.
When you're drawing hair, draw the low-light areas, or the shadows, that way you can layer thick color in, and thick shading. You can do a light outline of where you want the hair, but use short strokes to get the idea of loose ends that aren't quite fitting in perfectly.
You should always have one area that's softly connected to the face as well, somewhere that doesn't have a full dark line between the face and the hair, this will help make the hair look like it's not a wig. It is usually somewhere around a temple.
As for your latest project, you've got the angels of the fingers making them look broken. Try taking a picture of your hand and drawing it from that reference. It'll give you a single vantage point. It looks like you've discovered hand anatomy, but you're making everything in the hand look like it's flexed all the time, which isn't always the case. Sometimes the knuckles are going to be softer, and the fingers are going to point and flow rather than dig into things.
If you do quick sketches of the hand in all sorts of positions you'll get a better idea of what works naturally and what doesn't. Use your non-dominant hand for the reference.
