The bleed lines & border dimensions on where to keep the art. No one ever mentioned that in ANY type of comic making tutorial back in the day when I first started, so I was drawing stuff larger than it should've been.
I dont draw it the "first time" when I initially draw the thing in my comic, but I dont draw it 100 times enough. I may draw a thing 2 or 3 times before "BAM"- I throw it in my comic.
The number one thing that I still bitch & groan about today- COLORING. I do okay in certain zones- and I'm still learning, but I wish I could learn a LOT more faster. There are some days where I hate my coloring.