The popular themes in Shojo Manga are; romance, school, magic, costume drama, and comedy. Shojo are fully of symbolism - otherwise inanimate objects taking on special significance, as symbols or metaphors for something other than what they actually are. For example falling leaves, breath on glass, the ticking of a clock, falling flowers or hearts, or even the weather are all methods used by artists to give a scene a particular mood..
But not all romance,emotional and beautiful manga must always be shoujo.
Sailor moon is a well known shojo manga, where as examples like Love Hina and Ah! My Goddess are mistaken for shojo manga because they feature female characters prominently and/or feature romantic relationships. Most can be enjoyed by girls and women, as well, but the original intended audience is male. If the leading male is an unremarkable Average Joe (e.g., Oh, My Goddess, , Love Hina, etc), then you can be pretty sure it's not shojo manga. In shojo manga, the heroine is often an "ordinary girl," but the leading man must be tall, handsome, and cool.