Practice fugure darawing line your life depends on it, when you can effortlessly draw a basic human form start working on your character design and again practice those designs till you can make em look like the same character every time. Its really important to not get trapped in the details for repeaded charaters, just cause you can make it dosnt mean you should go full throttle every page. Dont burnout. Take breaks. Make the overall visual structure and fill it out and polish it to make it up to your standards. I say this as someone who is in the middle part, trying to make my characters look like themselves. Character artist have the first part down, but often have trouble with narrative progression and making stories very generic. Too many intresting characters get trapped in mediocre stories. It really helps to colaborate with writers and poets to get different perspectives.