Replying to Sketching/drawing

alright, so i've been really starting to get into art and stuff. recently i've been sketching some. but...more of like copying and taking other ppl's works and combining with others. and i like to sketch not like cartoons and stuff but more along the lines of what u'll see with graffiti. i've searched a ton already (and on graffiti forums) on how to start sketching these characters...but no luck. so any tips or links? o and not characters as in the alphabet, characters as in ppl, animals, that stuff