Adventures are made up of stringing encounters together. If you want a good adventure, you need good encounters.
It is an easy trap to fall into. For example fighting monsters just because they are there can be fun. But it also can get old fast, especially if there is no real reason why you are fighting.
The Angry GM has four tips to make encounters not suck.
http://theangrygm.com/four-things-youve-never-heard-of-that-make-encounters-not-suck/
1. At the start of each encounter ask yourself a dramatic question that the PCs don't necessarily know the outcome to.
For example, can they defuse the bomb before it goes off? Can they escape the cave before the troll finds them? Can they get the suspect to reveal the location of the mob boss hideout?
If the question isn't interesting DONT DO THE ENCOUNTER. If they have to get past a slide don't mistake it the question how can they kill the spider. They are not the same.
2. The encounter requires some sort of opposition to make it interesting. This could be a person, monster, trap, or even the environment.
3. There needs to be some sort of interesting decisions to be made by the PCs. If they run out of practical decisions or if they just keep doing the same thing for no reading then it is time to end it and move on. It is interesting if something changes as a result of the decision.
4. Provide some structure so you know how things are going and how to answer the question. Like tracking distance in a chase scene.
