I’ve put together a list of ten tips and tricks you can use to add some flavor to your game when creating and portraying the NPCs that interact with the PCs. The NPCs, after all, are what actually lends most of the depth and character (pun intended) to a campaign world during play. If they’re all cardboard cutouts and cookie cutter clones, the game lacks a lot of the flavor that might otherwise make it memorable.

When you need inspiration for how to imagine an original and unique NPC personality, draw examples from co-workers, classmates, and other people not among your fellow gamers and their friends. Obviously, if your fellow gamers and their friends are your classmates, you may have to adjust the list of candidates to exclude them. This keeps your NPCs from merely being the result of spiteful and mocking caricatures, or from accidentally insulting someone — among other potential problems.

When you want an NPC to provide a humorous reference to someone familiar to your players, draw inspiration from celebrities (and the characters they play, if they’re actors of some sort).

You might also draw inspiration from pictures you’ve seen. Visual stimuli such as paintings by talented fantasy artists serve as excellent grist for NPC concepts.

Build concepts off characters from non-fantasy fiction. My favorite example is actually that of a PC being inspired by the idea of playing a Batman type of character in D&D. The idea was initially to play the concept as a paladin, but by the time we were done with it the player had settled on the monk class.

Avoid silly voices. If you’re a talented enough actor to actually fit unique mannerisms and speech patterns into portrayals of NPCs without hamming it up too badly, go for it — but unless your intent is to run a comedy game, you might want to avoid doing a campy overdone French accent or doing the Diablo merchant’s Scottish “Wot c’n ah dew fer ye!?” brogue. In most games, it’s better to have an immersive atmosphere to your game than memorable cartoon voices that break the mood of a tense encounter by either embarrassing yourself or making people snicker at your Bill Clinton impression.

Get some detailed information about your players’ characters’ personality quirks — pet peeves, potent desires, strange habits, and so on. Draw inspiration from them when making NPCs. If you think you’re weak at making NPCs who will disagree with or stand up to PCs, focus a little on NPCs whose pet peeves match the PCs’ habits, and vice versa. In general, just find ways to play on the PCs’ personality quirks via your NPCs.

Make sure your players have some kind of idea of their characters’ backgrounds. Consider that, every once in a while, a coincidental meeting with someone or some thing from a PC’s past can add some punch to an encounter — or create an entire encounter in and of itself. If you suddenly find you need to save the PCs from certain doom because everybody was rolling poorly while you kept rolling 20s for the kobolds they were supposed to be able to wipe out in short order, using someone from a PC’s past as your deus ex machina to rescue them (and subsequently to draw them into some other adventure hook, thanks to this chance meeting) makes you look like a GM who plans ahead brilliantly rather than one who is really bad at fudging rolls effectively. This also shakes loose the usual expectation that all background NPCs are enemies, murder victims who must be avenged, hostages, or forgotten entirely.

Keep track of your PCs’ chance meetings and NPC traveling companions. The fact someone is no longer part of a given adventure doesn’t mean he or she can’t show up again later and lend some familiarity and color to the game. Just as the game can be made more interesting by bringing in NPCs from a character’s background, so too can you do the same thing with NPCs from earlier game sessions who “just happen” to be in the same part of the world. Such NPCs from earlier sessions can also serve as more deus ex machina saviors — and an earlier session’s friend might be more fun if he or she turns up later as an enemy thanks to unfortunate circumstance, lending some humanity to the PCs’ foes.

Let an enemy get away now and then. They don’t all have to fight to the death. Plan out escape tactics in advance for NPCs, and trigger points (maybe having lost a certain number of hit points, or a certain number of rounds having passed, for instance) for fleeing. Keep in mind that even if your PCs are getting their butts kicked, the enemy is probably also unhappy with some hit point losses (or even friends dying around them) — so you can save your PCs from accidentally overpowered NPCs by having the NPCs flee. Then, for an interesting twist on the recurring NPC idea, maybe you can have a former enemy show up later and save the PCs’ collective bacon because the former enemy happens to be on the same side of a new and different conflict.