If I am at all an expert on planning, painful experience rather than astounding success has brought it about. I am learning, however, and I think I can share with you what I have learned, which is basically this: Begin by understanding the purpose of planning.
The purpose of planning is not to hem you in, not to make you toe the line and meet schedules, not to inhibit all those impulses to follow sudden inspirations. The purpose of planning is to eliminate dithering, to free you of small daily decisions and to disengage your mind from concerns other than the one immediately at hand. The purpose of planning is also to assure you, before you begin, that you actually have something substantial worth writing. If you are an impulsive writer constantly beginning with great ideas that somehow dwindle away into nothingness and have to be abandoned, you may need to plan your work, simply to find out whether you have anything there to write. If you can’t put the gist of it into some kind of outline or statement, maybe you don’t have any gist: and it’s better to find this out before you start page one rather than after you finish page twenty.
But all plans should be flexible and roomy. Work should be planned flexibly enough to allow the mind to play and move freely. Time should be planned flexibly enough to allow for diversions and delays. Rigidity and creativity are incompatible. Cast-iron chapter plans and cast-iron schedules for writing them are fine — if you have to be a talented computer. If you are human, something closer to Play-Doh or Silly Putty would be more suitable.
The virtue of planning is that once you have an outline or a schedule made, you can give full attention to the page in front of you, knowing that you have allocated and organized properly for the pages still to come. In other words, plan ahead — and then stop looking ahead.