You’ve got to have conflict in your story. The protagonist has to have something – or someone – s/he’s fighting against and fighting for. Your supporting characters need to have their own agendas and it’s vital that they don’t always agree with the protagonist. You need that conflict to move things along.
Easier said than done sometimes. If you’re looking for some insight into how to make believable conflict and tension, here’s some reading material to give you food for thought:
Don’t forget, whatever obstacles you’re throwing in the way, they need to grow, and they need to do so organically. You can get away with a surprise every so often, but that needs to be believable, too. Keep it grounded, keep it real, and keep it coming.