35 Cheap Tricks

In response to Phlox, some cheap refereeing tricks.

1. Have some npcs that are nice, have them invite players to tea, show them hospitality. It'll make the dangerous and duplicitous parts of the world stand out more and endear npcs to players. 
2. Colliery to above, have weird or scary npcs that are nice, nothing makes an encounter memorable like a giant eldritch demon-spider inviting players to a tea party.
3. Seriously just have more tea or coffee or brunch parties. Having discussions over meals keeps conversations with npc's more interesting and can provide some fun setpeices. They can even be tense or hostile.
4. Theatre and plays are fantastic ways to deliver information, world build, and have some fun. Also have your players exploits be turned into comedic theatre once they become sufficiently known.
5. Give items, locations, objects, and such personalities. Perhaps as explicit spirits, or even just in a 'my rusty umbrella can be temperamental when I try to open it'. Anthropomorphizing things quickly fixes them in peoples minds. 
6. Give players a goodly but finite quantity of explosives, it will wreck so many things but its worth it.
7. When I doubt, roll a d6, if the number is higher events are favorable to the players, lower and its bad for the players. Super handy oracle.
8. Overemphasizing things can be good for some levity and to really reinforce an idea. 'It's a really big pig, like really really big, really really really big, this is just a whopping huge pig.' 
9. Sometimes fights should just devolve into cartoonish masses of flailing limbs that resolves when the dust clears.
10. Have crowds gather when players do unusual things in populated areas. Have them heckle and provide un/helpful advice. 
11. Sometimes having the consequences of a fight be being beaten up and robbed of all their belongings is better than death.
12. Travelers on the road might buddy up with players for a while if their going in the same direction, for safety and conversation.
13. Have players overhear npc conversations more often as a way of imparting info, it also helps make npc's feel less like information-kiosks, and can let players in on details about hostile npcs that they might not easily get otherwise (such as that these minions are dissatisfied with their boss).
14. The Men In Black can fit into nearly any game.
15. Have players get stuck, in squeezes, on thorns, in mud, and so on. As consequence, hinderance, and flavor.
16. Throw in little details to spice up combat, instead of the player just successfully hitting their opponent, they press the advantage, causing the brigand to slip on a patch of moss, and surely driving their blade into the brigands heart. And so on.
17. Likewise, let both players and npcs and monster all get caught out in the middle of doing things.....
18. Have npc's who hold grudges and act upon them. That street thug the players slighted is going to jump them with his buds the next time they come into town.
19. Concealed weapons and hidden pockets are excellent fun for both players to have and npc's to use.
20. Secret doors, hidden pockets, and so forth should always have some outward sign in the description letting you find them.
21. Describe what happens to leftover food, or prompt your players to.
22. Giving monsters and npc's a gimmick upon death (like exploding) is good fun, especially if more than one entity has it allowing players to learn it and potential exploit it.
23. Put at least one big buff boisterous man who sounds like Brian Blessed in your game.
24. Hair standing on end is handy for conveying powerful magic... or electricity. 
25. Colors are a quick way to flavor and name things. The Purple Barony. The Greenfolk. So on.
26. In-world lurid or saucy literature and songs are good fun.
27. Weird fish are a great way of adding subtle flavor to the world. Casually describe a fish market full of coelacanths and radiodonta.
28. Slightly uncommon but historical currency names are great for flavor. Get some ducats in there.
29. Give players unreliable information, but let them know its potentially unreliable so they can choose to act on it or not. Out of date information especially is useful as players know its potentially going to be misleading but can they afford, or even get up to date info?
30. Give npc's tics like eating something, chewing on something, fiddling, tapping, pacing, and so on, it characterizes and is easy to remember to include in description.
31. Let npcs be overly enthusiastic and brash, remember that some people are in fact the kind of person who'd join a bunch of strangers in doing something dangerous and stupid.
32. Locales, people, and monsters are almost universally improved by the addition of some incongruous element you wouldn't normally think of. 
33. Don't forget that teeth can be just as useful as hands.
34. Don't forget to describe what languages sound like in addition to what's said (in general terms of course, don't go full conlang).
35. Give players split second moments of reaction and oh shit as things go bad, traps go off, bushes are sprung, wrong levers are flipped, and so on.

Might do some more! They're very fun and also useful. I particularly loved Phlox's number 4, color coding things is just such a useful trick that I do not use enough.