In my experience, having a 1 page cheat sheet for each session has benefits that far outweigh the time that it takes to build it. I recommend creating a unique sheet for each session, a new cheat sheet for that specific game.
Plot Hooks – You should create hooks for every session, not just the first adventure. You want to get ‘buy in’ for each game so that your players and their characters really care about what is going on in.
Locations/Encounters/Scenes – Depending on the structure of the game system you’re using, having a bullet point list of the locations such as dungeon rooms, waypoints on the road or unique places can be a loose guide to keep your game on track. If you’re running a more crunchy dungeon delve style of adventure, having a list of probable encounters is just as valuable. As a storyteller, I find that having a list of possible scenes provides me with a loose framework for the story. Bonus Points: Create a scene tailored to put each player in the spotlight.
Important NPCs – Have a simple list of NPC’s the players are likely to encounter. Include details such as race, class, profession, a basic description, and simple motivations. For more NPCs that are vital for the story, you may need a social interactions tracker (doorways, reputations, influence levels, etc). Bonus points: add an identifying trait or quirk.
Previous Session Summary – Give yourself a high-level overview of what happened last game. This doesn’t have to be too long, but it should list the main plot points. Bonus points: ask a player to tell the group aloud their version of the events of the previous session before starting the game. You can pencil in anything the players focused on but you forgot.
Timeline – Depending on the type of game you are running, a timeline of past events, present happenings and possible future outcomes could be invaluable. A good villain has organized multiple schemes and the consequences of the players’ involvement is vital. If the players ignore what is going on, you need to know how it will affect the world. A timeline is 10000% necessary in any game involving time travel.
It does take a little time and effort to generate a cheat sheet for each session but the game will go smoother. It also helps alleviate stage fright. You’ll be prepared and you’ll know it.