Crow, check the stickies.. there are a couple good ID threads.. with EXCELLENT explainatations of what to look for.
for Juvies, especially in a stressful LFS situation, it is VERY difficult to tell apart orino, ocellaris, and kelberi and also Mono but they have a slightly different shape. it is also difficult to tell apart temensis and pinima at tiny sizes especially when they are stressed.
the best way to tell is to buy them, bring them home, joint the addiction and wait till they are healthy, happy and settled into their new environment and then compare them to the pictures in the stickies ID threads. Or ask the good folks on this forum to help ID it for you. with time you'll figure it out. it takes time and practice looking at different fish and you'll still get some wrong even years down the line.