One of the best things I think you can do is to use physical notes, handouts and objects in your game. For example, in Curse of the Black Pearls I had a bloodied note that some pirates had hastily written after they got ambushed. To make the effect look good, I hand wrote the note, crumpled up the paper, splashed some red paint on it (to resemble blood) and then to complete the effect I tore chunks out of it. So it looked quite convincingly like an actual old torn bloody note and then gave it to the PCs (instead of say, reading the text aloud or similar).
A great thing about writing things down like this and just giving PCs an actual diary, pages or whatever is it lets the players judge it in their own time. Written notes can be easily compared with one another and sharp players might be able to infer clues you’ve hidden inside for themselves if given time to think about things. It also helps to speed up the game when you aren’t sitting there reading large blocks of monologue like text out to your players.
Another very effective way to make use of these sort of hand outs is giving the players “In universe” drawn maps. In this case an NPC has drawn the map according to their understanding of things, which might vary between extremely accurate or just outright entirely false or wrong. Aside from being a great way to characterize a character, such as an old adventurer who hands the PCs a map only to discover that bits of it are entirely wrong or changed, it also feels more authentic when it isn’t so “Word of God” (so to speak).
Finally consider the use of actual real life board games, card games or things like tarot decks or similar. Players will be much more engaged with an NPC reading their fortune if you can pull out an actual Tarot deck and do it. Especially if you’re clever about it and stack the deck (no pun intended!) in your favor so you get the right results for the players characters! Another good example is using an actual board game like chess, checkers or similar to illustrate a point or just play. If you’re not confident on these games yourself, computer programs are a very very good way of “cheating” to make an NPC seem much more intimidating (depending on how good your players are at this game).
Sometimes physical objects can be good if you can acquire them or get access to something suitable. For example in Masks of the Dreamer I was really hoping to get an actual sextant for the players to look at and even physically use. Alas I couldn’t really find one that was suitable and for a decent price, but in the past I have used actual puzzles, statues and similar physical objects to represent in game artifacts/items. Doing so helps ground something in reality and provides an immediate tangible item for your players to fiddle with.
Most recently and inspired by something I saw on Pelgrane Press’ “See Page XX“, I have decided to have a go at making my own book using the advice they gave. Further updates in this series will be posted as I go about creating it! Plus how my players receive this particular piece of work will be most interesting. It will be a big project, but if I can pull it off I think it’s going to add a very great feel to my Trail of Cthulhu game to have their very own mythos tome to look through. Plus it will be a great asset to have for future games as well.