I really do have a plan when I write my fiction. But it is not by any means set in stone. What helps me avoid writing myself into a corner is the fact that I know my characters. I know their strengths and their flaws, I know what they would likely do in a given situation. So whenever I feel like "What do I write now?", I just let the characters choose. It's really quite cool because the story takes on a life of it's own. Things happen that you did'n't even plan to happen.
I really think that it is improper to force a plot on characters and expect them to act accordingly, they should ACT according to how they feel and what they are, just like in real life. Of course if your writing comedy, feel free to ignore that. But consistency is very important with writing characters I believe.
I believe ANY story can be interesting if the characters are. Say your character just wants to make a peanut butter sandwich. While that premise may seem silly, I assure you it is quite possible to make an epic story on that; albeit likely filled with comedy.