Have a start and a goal, and maybe some events that you want to happen in between and leave the rest up to the players.
Start - you put the players in a cave, tied up, having been abducted by some hobgoblins who revere a beholder as their god-king. They plan to feed the players to it.
Goal - The players survive.
The rest is up to the players. They can magically control a hobgoblin (assuming they have the ability) to release them, or start attacking the other hobgoblins as a distraction while they untie themselves and escape, they can wait until they are to be fed, then kill the beholder, now having their own clan of loyal (and scared) hobgoblins...
What I am trying to say is, don't first think of a whole adventure that you want to run, with all the details in it, and then find details to remove to make it interactive - make it interactive from the very beginning.
While writing the adventure, always keep your players in mind - One of them might not actively take part in the RP, but is an excellent tactician and shines in battle. In that case, have some battles with tactical elements (cover, height difference, changing battlefield - like a bridge that collapses, or magical platforms that fly around the scene that the players, but also enemies, can stand on). One other might prefer to flesh out his character, and thrives in conversation - have a pivotal point of the adventure involve conversation and diplomacy.
Whatever you do, if you know your group and keep them in mind when developing an adventure, the players will (in my experience) find ways to do it their way. I find, you might create an encounter, or a story, and expect the players to do certain things within that story, but they will always think of something you haven't planned for.
Listen to your players.
Have an open mind. If the players suggest something you haven't planned for, improvise it. Give them what they want. You can't plan for every possible action they might take - so judge them while you play, and see what ideas they come up with - then make it work within the story you have prepared.
Create your story as if it were a tree. You start at the trunk where certain things happen, then start creating branches according to different things that might happen.
Don't try to cover every possibility, but rather, during the creation process, make branches that you can adapt to what the players might do. When you are writing the "branches of the tree" think of results, what that branch does and what it means for the players, not how they will get to it; they will find a way on their own.
I know I possibly overcomplicate the answer, but I hope I've helped :)