David visits lots of art schools around the country and sees students' portfolios. There's no end to the amount of creative ideas being produced out there, David says, but the problem for new illustrators is their technique.
It may sound very basic, but if you are being told in portfolio critiques that your people don't look all that great, GO TAKE A FIGURE DRAWING CLASS. Figure drawing is tough, get over your fear, and don't worry about showing your figure sketches (Don't! says David) or having it look good until you've drawn 100 figures.
If your characters aren't necessarily human, be sure you find photos or real life examples and do your research -- for TUESDAY David found frog skeletons to reference.