if youre a beginner, i would say right cheek, left cheek....etc.
if you get sore, try the quad or delt. i think the delt shot is easier than the quad, but some will say just sit and shoot.
i did a few cycles with just glute shots until i decided to try other injection sites.....the "build up" of scar tissue is not a myth, but it doesnt come as quickly as some will tell you.
if you are using fast acting esters, you need more shots throughout the week...ie: everyday or every other day. then i would say rotate glute, glute, delt, delt, quad, quad, continue....
slow acting esters....just do glute, glute with a larger number gauge needle. larger gauge = smaller needle. ie: 18 gauge needle is HUGE...23 is perfect...