I'm going to be running a wilderness exploration. How do you go from one encounter to the next? "You travel for three more hours, and then x jumps out. Roll initiative." I'm exaggerating, but how should I introduce an encounter better than "a thing happens"?

Introducing an encounter can be easy if you know how to ramp up tension, be descriptive, and seem like it wasn't "planned."

I usually have my players choose someone to be the scout and have that player roll perception checks occasionally. I choose an arbitrary DC and if they fail it, they have an encounter. Have them pass someone shady looking on the road who decides to turn around and engage the party. Have bandits on the road ahead of them demand a toll for them to pass. Describe them entering a particularly heavily wooded part of the path and they hear strange, bestial noises all around them. Have it start out singular and soft, then slowly get louder and more numerous. 

Is there a reason the group is traversing the wilderness? If you go into a BBEG's territory, depending on what kind of creature it is, the environment will change. Natural hazards will appear. Nature trying to slow down, poison, fight in a skill challenge format against the group. Weakening them before even encountering combat.

You can create combat encounters that make sense to occur on the journey. Make it part of just regular combat encounters, but its optional to use or not. And you can drop them in whenever. Similar to Random Encounters, but not quite.

When going through the woods/marshes from the city to the "dungeon".... I use 30-60minute in-game intervals. Asking the players what each character does. Keeping eye out for danger, or perhaps doing some herbalism/scavenging etc. So if the group goes to find herbs/roots in a certain environment. Then you could also drop in an encounter that would fit. However not every hour an encounter has to happen of course. They could also run into an animal to find someone who can bury the corpse of his ranger master or some other event.

Thanks, you two.

Could have the first encounter happen during a watch at a rest. Then, when they kill it, perhaps a natural predator in the region is trailing them due to the blood and scent. Having those who are proficient with survival or are used to this sort of environment (aka not all the PCs usually) do occasional perception/survival checks to see if they notice that they're being followed, but only finding hints of it - pawprints, the remains of a predator's meal, tufts of fur, broken branches. Building it up like this is actually an "encounter" in itself - a series of skill encounters while building tension.

Then when they are finally ambushed by the predator, or locate it, fight it, whatever, during the fight-encounter or after when they're harvesting it, have them notice something "a bit off" about it. Acting wrong, more hostile than usual, some strange physical thing. Build up the idea that there's far more going on in this area than you might think normally. It might tie into your main plot/adventure, or be a side adventure they could eventually explore. Your PCs might even then try to keep their eyes peeled for other creatures acting odd, which could turn a simple "hunting deer for dinner" thing into its own encounter when the deer is also off.

Nice, thanks :D

Quote from OboeCrazy >>

It's perfectly OK to say "You travel for another four hours without issue, and then..." because that's cinematic. 

I.E. don't be Robert Jordan ;)

I'd start by defining your wilderness in clearer terms. What is this place? What are its unique characteristics: flora, fauna, terrain and other features? What sort of things happen here? Is it completely isolated, or are their occasional signs of a humanoid presence (even if it's just ruins)?

Then, take these defining features and prepare some short descriptions of them. Things that you can use to remind your players where they are and help convey the feel of the place. This should help ground the party, so it's less point A to point B.

When you're creating encounters for wilderness exploration, it also helps to break up combat with other events and discoveries. Maybe it's just finding a unique landmark: a rock formation, an old ruin, a forest shrine. Or spotting some wildlife that isn't hostile. Or discovering a hidden treasure cache. Or an overlook that captures a beautiful view of the wilderness. Minor hazards like biting insects, venomous plants and animals, inclement weather, etc. etc. All of these things can help make the travel and exploration feel more immersive.

You should also consider the story you're trying to tell with this journey. Is this a slog through a terrible swamp? Or a trek of wondrous discovery through an ancient forest? What's the overall vibe you're trying to communicate to your players? If the wilderness is truly dangerous, there should be many hazards and combat encounters with a few discoveries. If it's less dangerous, maybe there's only the occasional combat, but more non-combat encounters and other events. Also, consider how things going on in the rest of your story might affect the wilderness the party is traveling through.

As for the actual combat encounters, I'd suggest telegraphing them a bit beforehand. Few monsters or other creatures are going to leave no sign of their presence. Maybe the party encounters tracks, or old bones, or other markings long before they meet the actual creatures themselves. Maybe they hear strange calls in the night as they're in their camp, but they don't see the creature until days later.

Also, I'm not sure if you're planning to use random encounters, but I'd suggest avoiding this, especially the old "one random encounter per day" trope. Instead, randomize the timing and type of your encounters (combat, social, other discoveries, etc.), but plan all these things beforehand. It's not too hard to prep a couple short ideas for combat and non-combat encounters; you don't need too much, just the core idea of the encounter and maybe some quick descriptions (and stat blocks to use, if applicable). But by thinking about what encounters make the most sense in this environment and the story you're trying to tell, these "random" encounters will end up being much more evocative.