Conflict!
From Janice Hardy's The Other Side of the Story, some great advice about pacing and plotting your story:
1. Use all three types of conflict:
Your hero should have a difficult internal conflict, relational conflict with other characters, and an external conflict against his environment or circumstances. Developing all three strands of conflict gives your story depth and keeps your reader constantly invested in reading more.[...]
4. Pacing:
The pacing of conflict in your story should look like this: Conflict Simmers » Conflict Boils » Conflict Explodes » Breathing Space » Repeat as necessary.
5. Pacing #2:
All of that simmering, boiling, and exploding should look like peaks in your manuscript while the breathing space looks like valleys. Your peaks should get progressively higher and higher as the story nears completion. If you have two or three peaks in a row that are all at the same level of risk/intensity/stakes, you aren’t at a peak. You’re at a plateau, and you need to reassess those conflicts and figure out how to escalate them.[...]
7. Have inner and outer conflict meet:
When your hero’s choices in how to face his outer conflict lead to increased inner conflict (isolation, fear, guilt), you’ve done a good job of escalating the conflict.
Read the rest here!