As a geek and an amateur illustrator of dinosaurs, among the mostr frustrating and most difficult thing to draw in the right way are the wings of Aviremigians (i.e. the clade that includes Yixianosaurus, Oviraptorosaurs and Paraves). Expecially when they're folded. Rarely you can see good reconstructions in this regard. The most common errors are the orientation of the feathers (generally in a very chaotic way) and that of the wrist. The latter in particular is the most relevant. The wings of most species more primitive than Aves are different, although at first strikingly similar. How to get them right then? On my blog, I give some useful tips to know how to restore them properly, but in an amatorial way.
1. Bare naked. 2. Arm feathers. 3. Hand feathers. 4. Final result
EDIT: corrected some terminology and added thoughts on scapulars.
References: Scott Hartman, The asymmetry of the carpal joint and the evolution of wing folding in maniraptoran theropod dinosaurs, Animals Real and Imagined by Terryl Whitlatch
I've always found the reference material for folded maniraptoran wings has been extremely difficult to come by. Even reference material for wing folding in modern birds is strangely difficult to find and decipher. This image is both great looking AND helpful! Thanks!
I wonder about scapulars. Just realizing this from your great tutorial here, but I wonder if there's been any argument for or against larger scapular feathers.