I have tried 2 different plot methods in the past. 1. an outline where I connect plot points from beginning to end all written in advance and 2. an intro with no direction that organically goes where ever it leads me. I can't say either one is better, but the second one gave me more creative freedom to make changes as the story was written. But the first one made sure I hit all the high points I wanted to cover. I guess it's like throwing darts at a dart board. Who knows what you're going to end up with. My next idea is to sit around with friends and have a group plot chain where we come up with the back bones of a story and I go home and flesh out the details. That way, since the story was created by committee, it has a better chance of being accepted by a more diverse group. I also write music and find the songs I collaborate with are better than the songs I create on my own.
My approach falls somewhere between these two; a hybrid, if you will. When I start out, I have a starting point, an endpoint, and a handful of key intermediate touchpoints. But I don't map out my plot network in advance. I let characters drive the flow of the story, and I introduce events as needed to nudge the storyline toward the touchpoints/endpoint. Or away, if the story is flowing too smoothly, too easily. As you point out, the lack of detailed planning results in more creative freedom, and also a more organic flow. Also, because my characters are also minimally defined at the outset, my characters grow organically as well. I'm not saying this approach is best for everyone. Many writers seem to prefer a more structured methodology, so they know exactly where they are in the story at all times. I only know what works best for me.
I have found that doing a plot works great when you involve other people. However, anything more than yourself and one other person can become a bit confusing. Things start to become quite complicated and people tend to piggy back too much into the meat of the story. So my suggestion is, if you include others in your plot development, don't use too large of a crowd to bounce ideas off of.
creation by committee is probably what produced the absurd-looking platypus... having a single collaborator is one thing, if you work well together, but making a literary stew out of what everyone in the room tosses in the pot isn't likely to result in anything but an indigestible mess, or worse...
There is no way I could ever collaborate in any aspect of writing. My ideas are mine, my characters are mine, my plots are mine, my prose is mine. If I include someone else in the writing, the story stops being mine and I completely lose interest. I need to stand or fall on my own.
Like Cog, I sort of do both - I have a general idea where I'm going but I'm open for a detour sign. If my characters want to do something I hadn't planned on them doing, then I let them just to see where they'll take the story. Most people don't believe that a character can actually take over a story and surprise you but they can if you let them. Usually, it's when a writer is so deep into creative opportunities ( imagination ) that the plot line and planning goes kabluey and fresh ideas take over. The bonus of a fresh idea - is that it usually won't be as predicable as what was planned. Your subconscious is always one step ahead of you planting little seeds to pull it all together.
I write down a list of plot points to develop the plot so I will know what to write without getting a Writer's Block.
Drinking a two liter of Mt. Dew before bed time and laying there with lights off and insomnia works too. You would be amazed how much of your plot you can fill in during that time.