One aspect in which two Dungeon & Dragons campaigns with different Dungeon Masters are likely to differ a lot is the amount of preparation, the work done between play sessions. Some DMs prepare very little, and then either invent things on the spot, or follow some printed material. Other DMs spend more time preparing than actually playing. That is not only a matter of personal preference, but also related to your play session schedule: If you play often, you don't have time to prepare very much; if you play rarely, preparation makes sense, because you don't want to lose valuable play session minutes with stuff you could have prepared before.

As I am in the latter situation, I tend to prepare a lot. Some of that is story preparation, knowing your NPCs, their motivation, and how they will drive the story forwards with or without the interaction with the players. But of that type of preparation you can only do so much: The story mostly evolves while playing, and you don't want to smother the evolving story by the prepared one.

So a lot of my preparation tends to be on the technical side, like having battle maps, tokens for the monsters, initiative cards for monsters and players, initiative riders to place on top of the DM screen to show turn order, character sheets, powers, and so on. And I'm always looking how to improve that sort of technical preparation, because running combat faster and smoother is always better than having to scramble for information during the play session.

One trick I just recently picked up from watching the D&D videos on YouTube is using trading card sleeves for D&D power cards. While I played a lot of Magic the Gathering until about a decade ago, I wasn't as concerned about the state of my cards as many collectors were, and I played without sleeves, to the horror of some of my opponents. But as many people use these sleeves, they are widely available, and you can get them in different colors. So how does that help for D&D? Well, every character class has powers, which originally come printed in a book. But there are various methods to get those powers into card form, for example the official character sheet generator from Dungeons & Dragons Insider. For my French speaking campaign I use a program called CardsGen, and I'm sure there are equivalent programs in other languages.

By putting the power cards in the appropriate color of sleeves, you can easily keep track of your various encounter and daily powers, by turning them around when you used them. After combat you turn the red ones back up, and after an extended rest the black ones. Green sleeves are for at-will powers, and I use blue sleeves for racial and class traits. While printing out all the powers of your characters and sleeving them takes some time, I'm sure I'll gain time with this system where it counts: During my play sessions.