You start with a premise, a truth about the world you believe in. Like, ruthless ambition leads to self-destruction (MacBeth) or The greatest love defies even death (Romeo & Juliet). More modern versions would be, sacrifice and honor lead to triumph over intergalactic, violent robots (Transformers), being true to yourself leads to great burgers and making out with a really hot neighbor (Harold & Kumar), being right makes you a great doctor (House MD).
You need really developed characters, as they drive the story and keep the plot moving. Characters can be explained via physical, sociological, and psychological characteristics. The protagonist/hero must want something so badly he or she is willing to make difficult choices to attain that thing. The antagonist may want the same or similar thing, and thus presents him/herself as the obstacle to the attainment of that thing. Without great passion, there is no story.
I guess more broadly speaking, what do you really want? But something you want so much you'd be willing to give up something else you also like/enjoy, as well as work and strive to fight in order to get that "thing"? Obviously this question could have been worded more concisely but you get the idea.