After a while combat encounters get pretty boring. I mean, sure, you can spruce them up a number of ways. You can ambush the PCs, or have the PCs ambush the NPCs, or have it just be a straight up fight. It can be a fight for a cause, or just over money, or just because someone won't give right of way on a bridge. Eventually though, your sessions are just conversations and what nots until the next fight. At least, that's what my D&D game is right now. So today, let's talk about other ways to mix it up.
Combat Has A Point
First, let's be honest. Combat has a purpose and there's a reason it shows up in most of your games a lot. RPGs tend to default to Action stories, and it's the rare RPG that doesn't have the "Combat Mechanics" section be one of the largest sections in the game. This is ok. The idea here isn't to remove combat - especially if you're running a game where people expect it. The idea is to have other things to happen to make the combat stand out more when it does happen.
Traps and Puzzles
Traps and Puzzles are the second default encounter you'll get in most games - especially ones like D&D. Heck, the D&D Dungeon Master's Guide even points out that you should mix in traps and puzzles as smaller encounters. These are good ways to have lower lethality - maybe - obstacles in the way of the party where the challenge is more mental than the rigors of a combat check.
Traps can be as simple as a pit trap or a poison needle in a lock, and as complex as a room that will gas the whole area unless only certain locks are disengaged and the others left alone. A trap can even be a sign of age and not design, such as a bridge that has rotted out and will drop out from beneath the PCs when they try to cross it.
Puzzles can be anything from riddles to brain teasers to actual physical puzzles. Matching shapes, matching keys, matching blocks, or finding the right tool for the specific shaped valve can all work. The Resident Evil series is full of minor puzzles, and more major ones that can work and the internet has hundreds if not thousands of examples.
Chance Encounters And Sights of Wonder
An encounter does not have to be a big thing. It can be something small and world building. It could also be something that impacts how the PCs handle a current situation. For example, the PCs could come to a ridge and see a group of giants moving in a group from one camp to another, or perhaps waging in combat with some other type of creature. What do the PCs do? Do they wade in and get involved? Go around? Wait and see if they can loot the battleground?
Encounters like this can also be used to build the world and continue telling the story of various things going on in your game. Perhaps the PCs come across a group of soldiers from a foreign kingdom moving along a road. Perhaps later they find soldiers from the home kingdom. Do they get involved at all? If so, do they cause a battle to happen and warn of the invasion or let it go?
The encounter doesn't even have to involve living creatures. Coming across a ridge or crevasse and seeing statues of an ancient kingdom and a broken road that stretches across rivers of lava can be enough. Throw that in front of your PCs and what do they do?
Other People On The Road
Not every encounter has to be bad or negative. Sometimes the encounter can be good, or even helpful. Perhaps the party meets another group of adventurers on the road who are heading in different directions. The encounter can be a chance to share information, talk shop, and even get leads on potential areas that either group isn't going to go for but the other can avail themselves of.
Just the idea of other groups out there doing what the PCs do can make for interesting encounters. It can also be a tool you use and bring up again and again in the future to set up rivalry, make friends, and give the PCs some allies to call upon in times of need.