Determining wandering monsters' motive doesn't just tell you why they're wandering, it—crucially—tells you what they want from the PCs, and how they'll go about getting it. That's a lot of bang for your buck! (12/14)

Wandering monsters already have an activity baked in (wandering, of course), but we can add more dimension by determining their MOTIVE. The expanded reaction table that's been floating around for a while is a good example of what I mean—the needs inform the encounter. (11/14)

While surprise is a possibility, it's not guaranteed for every encounter. Some games even deny the possibility that monsters can be surprised by a party carrying blazing torches through the inky darkness of the underworld. (6/14)

Monsters hang out in a hallways, sure, but stationary activities are generally the purview of room encounters. Think about what happens if a random encounter is rolled while the PCs are in an empty room. This is why, traditionally, random encounters are rolled on a "wandering monsters" table. (4/14)

Encounter activities can be a great way to add color to random encounters. See Arnold K's seminal "WTF are these goblins doing?" table. Nowadays its even common to bake activities in to the encounter table itself. "2d6 goblins playing kiss the blowfish" is more exciting than "2d6 goblins." (2/14)

A lot of people conceptualize random encounters as the party encountering the monsters, but they make more sense the other way: the monsters encounter the party.

Below is a thread on what most people get wrong about encounter activities and what there is to be done about it. (1/14)

I also got to show my players the best monster art from 5e: