When you think of nice arms, you probably picture tight, lean arms without any excess jiggle. You probably picture arms with definite curves and shape vs an arm that appears to be more tubular shaped.
Now some women like a super cut athletic look, almost a little on the muscular side, and some like the “long lean” look with soft definition. Surprisingly, both are achieved with pretty similar methods (in the beginning at least).
Now how do you get ‘em? Biceps curls, Triceps dips? Yes, those are a part of it but you’re probably forgetting a muscle that makes all the difference – your shoulders, your side delts to be exact. You see, your side delt muscle actually takes up the top third of your 
arm and is one of the main things that give you that “separation” in your arms so that you have shape. Again, you can make that definition as strong or as soft as you prefer but either way, you’re gonna want to work those muscles if nice arms for the summer is your goal.