Only advice i can give is keep drawin... Peep other peoples work, peep some different styles and draw your ass off!
Just like can control man... people need pen control. Gotta know depth/perspective, light sources, good use of color, composition, etc.. etc.. Basic art shit... People forget Graff is art, and folks with 0 artistic talent think they can write and get good..
The best Graff artists are straight up artists. The other fools who make it are 1Dimensional writers who have two or 3 hand styles and 2 or 3 throwies. The only reason they make it in the game is cause they get up retarded.
People like JA, Ryno, Dr.Sex,Foe, etc.. etc..aren't good graff artists, they just bomb like crazy. That nikka doesn't have a lick of talent in him. No disrespect but thats a fact.