Popping in to relay a sweet tip I've just been given. If you take an image you've been working on and flip it horizontally, it becomes MUCH easier to find the faults. For example:
I had just finished this earlier today and was pretty pleased with it. There were a few issues I'd taken notice of: the pant leg on our left is a bit too wide, the slit between the legs is too wide and dark (resembling a vagina.) Additionally, the flow of the excess belt doesn't match the implied wind direction the hair is giving off. Beyond that, I was pretty satisfied with it. However...
When you flip the image, the faults are, for whatever reason, easier to see. As you can tell, the shoulder on the left of the flipped image is significantly lower than its counter-part. The bicep is also just a little bigger than the arm on the right. Beyond a few minor hand differences, there's the problem of the neck not being symmetrical, the eyes implying a direction I wasn't going for, and the lowest hair stems not matching each other.
I'm going to look into why exactly flipping the image makes it easier to find the faults, but yeah, a really cool little tip I stumbled upon. Don't take it too seriously, though. I've been flipping a lot of professional animator's work and noticing some imperfections (not as drastic as mine, but still existent.)