I know this topic is difficult for some people. For me, using this method has made it super easy! These aren't perfectly realistic wings by the way. I just find that they have a really good quick/quality ratio, that works fine for me when drawing angels or beasts or random birds.
If you're looking for really anatomically precise wings, check out these 2 tutorials: [link]
they just take longer.
So I'm sharing /o/. EDIT: Because some found this confusing, I'm explaining better what I mean by top/under, inside/outside:
"under-side" = stomach-side
"top-side" = back-side
"Inside" = closer to the body of the bird
"Outside" = closer to the edge of the wing = further from the body.
Beware randomly shaped birds in this tutorial and please note that if you want to make fantastically-shaped wings, you can! The main thing to remember here is the structure.
Please tell me if you find this useful, and don't hesitate to share your drawings if you use it, I'd love to see them!
Check out more of my winged art:[link] [link] [link]