I don't know why anyone would want to write fiction these days, since clearly it can and will be held against you if you ever run for office. (For a clear definition of what, exactly, fiction is and why it shouldn't influence your vote, see Susan Gable's explanation at Booksquare.)
But it has come to my attention that hordes of would-be literati will be attempting just that this month. Thousands of you have signed up for NaNoWriMo, a month-long novel writing exercise. (Why November is deemed the ideal novel writing month is beyond me, although it may have something to do with the fact that writers love alliteration.)
I am really torn: Should I offer my sympathy? My encouragement? My therapist's number?
The truth is, I don't have a therapist. I can't afford one. Not many writers can, since book publishers (if you are lucky enough to have one) don't offer health insurance, much less sanity insurance, and the measly advances would hardly pay for a decent shrink. Which you will need if you attempt to write a novel. Either that or a writers' group. I recommend the latter; they're cheaper and more effective.
The point is, if you're writing a novel because you want to get rich, forget it right now. You'll make more money, plus have benefits, if you learn to drive an 18-wheeler.
Writing a novel is extremely difficult. Writing a good novel is virtually impossible. If this is your goal, stop now. Very few perfectionists ever get beyond the first page.
Novel writing requires a completely different skill set than any other task you've performed. There have been thousands of how-to books written, thousands of workshops given, millions of articles penned (I've written a few of those myself), all dispensing very good advice. You can read them all, and still not know how to go about starting a novel, and more importantly, finishing it.
The best way to start is to just start, not at the beginning but in the middle. You can fill in the backstory later, you can explain why, where, and how pretty the sunset was, in another chapter, but you must immediately give the reader a reason to keep reading. You must make them care about your character. If you don't care about him or her yourself, then your readers won't either. This does not mean you must open the book with a scene where your character saves a litter of puppies from certain death on the freeway. Although...I could see it working. Hmmm...
As for ending your novel, you will end it when your characters have solved whatever problem they have. And there's a big clue right there: your characters must have a problem (more than one, hopefully), and bigger is better. No one wants to read about Jane or Jim's mounting pile of laundry (although dirty laundry can be symbolic). If you're a tidy person who doesn't like messiness (conflict, in the language of novelists) you'll never be able to pull this off.
Good luck to you. I'll try to offer encouragement as the month progresses, since I bet you haven't taken my advice and joined a writers' group. Consider me your writing coach. (I am very good at offering advice, very bad at taking it.)
Now pour yourself a cup of tea and write the first sentence. It gets easier after that.