Present conflict as early in the story as possible, but leave yourself ways to escalate the conflicts and the suspense factor along with it. Remember that a conflict must either lead deeper into the story or to a climax to create suspense and hook your reader.
Develop commanding characters for both the protagonist and antagonist. The protagonist should be someone your audience cares about, so that wondering what will happen to her creates suspense. The antagonist should be the type of character that is so devious that the reader cannot fathom what he might do to achieve his goals. This also creates suspense toward the fate of the protagonist.
Start with the final conflict and work backwards. This allows you to pace the story and create obstacles and problems that do not overshadow the climactic end.