How to balance big shoulders? (Female)?

I want to tone up my arms but my shoulder muscles inevitably get huuuge whenever I do. I read an article about balancing your muscles to get a sleeker look (For example, if the biceps are very large, work the triceps and sides of the arms). This seems like a good idea to me and I'd like to try it, but I don't know what muscles to work to balance/lengthen my big old deltoids. Any help?