My weakest points.

Try charting the plotline out before you write--perhaps make boxes that summarize exactly what you want to happen in the plot within a given chapter. Decide about how many words you want in each chapter (for example, around 2,500 in each chapter) I like to use this method because sometimes I need to remind myself of my original plotline. Be aware, however, that after you end up writing something, you might realize that your original plotline needs rewriting or adjustment. Just adjust it as you go along!

I have exactly the same problem. I can think of everything else but the story, and in some ways I think it's better because it allows me to be more flexible and I can change or add things depending on what I think. But the problem is the story, if it doesn't have a definite direction, can fly out everywhere at once and become confusing or pointless.

I can only give you the advice that I am using which is to think of the ending and the purpose. What are you trying to do with your story? Is it about making a point, telling a story; what is the purpose? When you know where everything is going, it helps you write toward that end and reigns you in a bit.