If you talked to anyone that played in one of my games, they would certainly tell you about some favourite tactics that usually appear in my games. These are a bit more macro tactics and never are implemented in exactly the same way from game to game.

1. Mystery – whether it is a mystery around a BBEG, PC, or NPC, there is nothing better than having a mystery within the game to be solved. Perhaps there is a lost lineage, a grudge that is being held, or a noble secret waiting to be told. Having this tension simmer below the surface can add so much to the campaign – just waiting to be revealed at the worst possible time.
2. The old double cross – There is nothing I enjoy more than having an NPC join the party and bide his or her time until the moment arrives. It has gotten to the point now where the players don’t trust me and I have multiple NPC’s come and go without incident just to keep them on edge. But when you can pull it off and surprise the party, there is nothing like it for DM and players alike. Having to define an NPC with a planned double cross always makes me create more depth in my NPC characters that helps to enrich the story. Having one-dimensional NPCs are required sometime, but being able to develop their motivations and actions to the level of the players can create tension and surprise for everyone.
3. The false ending – I learned this one from “How to be a Great GM”. It again has a little of the double-cross feel to it where you take a common BBEG and ending and really expand on it. Sometimes it involves really thinking about the BBEG motivations and understanding that the BBEG is more complex and there are other factors in play. They aren’t evil just to be evil. They are tortured and have suffered much in their lives. The pay off is if you can get the players to have sympathy for the BBEG and doubt themselves as they finally have the climatic encounter. “Are they really evil? Could I be wrong?”. A few times I even managed to get the party to decide if they will partner with the BBEG to defeat the true villain.
4. Shock and Awe – making it personal. It is easy to paint a BBEG as evil and needing to be defeated just because, but can you make it personal? This involves knowing your players and asking them the right questions in session 0 just to ensure you don’t offend someone. Often times I would pull things out of their backstories and perhaps resurrect a long dead lover to become a consort. Or perhaps execute a child, pet, or other character that the party has become attached to. Or describe a scene that is truly horrifying and surprising. The idea is to provide a surprise that reinforces just how truly evil the BBEG is and to enrage the characters to avenge those killed. Now if you can balance that anger with a false ending and doubt you truly have great story.