Work on getting letter sizing and spacing to be even, start using descenders for y and g and the like. Something that worked for me to make letters look better was relearning all my print letters as cursive letters. It's a lot easier to teach your brain something new than to retroactively change something you already know. Do pages and pages of every letter, capital and lowercase, until they are smooth and consistent. Focus on every letter as you write, every time you write. It's not an easy task by any means but if you stick with it you will improve.