Here is my very primitive take.
The basic plot, from the beginning of time with Beowulf and Gilgamesh, to Shakespeare and Silence of the Lambs and Pride and Prejudice, is:
1. Get your main character up a tree.
2. Throw rocks at him/her.
3. Get your main character down the tree.
Plot is:
- how you get your character up a tree. This is where plot begins: the character is forced into a situation from which he/she cannot escape through walking away, hitting the bar, ordering for pizza, etc.
- what rocks are thrown at the tree. This can be anything from hating Mr. Darcy to Grendel snacking on your men in the dining hall.
- how you get your character down the tree. Resolution of the rocks tends to do it, along with providing a rope or some other way to get down.
Character is:
- what personality in your character made it so that they would get up into that tree and can't get down? This affects how you get them up the tree; if you have a bear running around, only characters that cannot kill a bear, and are not suicidal, and do not have something to protect from the bear, will get up the tree. If you take away all the food on the island (if this is an island), then you can only get them up the coconut tree if they won't eat lizards and bugs or don't know how to fish (and, I suppose, don't hate coconuts more than life). Who they are also dictates how you trap them in the tree.
- who they are also dictates what kind of rocks can be thrown. Are they really good at dodging rocks? Find some honking big ones to pitch. Are they allergic to certain kinds of rocks? Throw those. Do they get really bothered by lots of little rocks constantly pelting them and wearing down their spirit? You know what to do. Try to get them out of that tree before they are ready to deal with whatever lies below (or deal with not having whatever it is in the tree that allows them to survive).
- who they are dictates how they can get out of the tree (safely). Someone who is always going to be scared of bears is never going to get down as long as the bear remains unresolved. Maybe they grow and become knowledgeable enough (say that there's a wood elf palace up that tree where they can train) to kill the bear. Maybe they are resourceful enough to build an effective gun out of coconuts and the little rocks you keep throwing up to create an especially deadly pellet gun to kill the bear. Maybe they become suicidal (a la Hamlet) and just throw themselves down to the bear.
If you want to implement deux ex machina, the bear suddenly dies of a heart attack.
Because character dictates plot---or at least that's how I see it---to me you have character first, then you derive plot from your characters.