How do i take designs in my cornrowin to a higher level?

i am 15 years old and i am great at braidng but thee basics.....crossing,swirls,zig zags,dollar signs etc...i want to take my brading to the next level shapes....stars, hearts,fish braids etc and my parting to be A LITTLE better...im askin for any advice or if so step by step instructions to parting it so i can do thee difficukt designs im really interested in thee stars...i seen soooo many designs on thee web and im sure its very easy....but how do they part it so you can do thee design.....?like startin in thee middle of the head its all about the parting i kno but do you have any way to make explaining it a bit easier?