Step one: turn off the television, unless the novel you’re writing is about watching television, in which case it’s probably better to turn it off anyway and make up the experience of watching television based on your memories of watching television, as opposed to a detailed play-by-play of you actually watching television, which would be like nonfiction anyway, but that’s more of a stylistic quarrel, I guess.
Step two: describe the ever-loving shit out of it. By it of course I mean anything, the day’s activities, the conflict, the history, the room your character is in, the character’s face/locomotion/wardrobe, the weather, the moment, the month, the year, etc., the politics, the economics, the biology, the food. Especially if you’re working in third-person, if you have a narrator, take advantage of this lucky choice you made and don’t underestimate the mileage you can get out of fleshing out every given aspect of your created world. (Note: for first person this philosophy still applies, but the foremost thing you have to be concerned with detailing is your character’s voice, as in the reason you’re writing in first in the first place. You should be demonstrating every looping inflection and every insight unique to this person’s mind that you possibly can. [Note note: if you’re writing in second person, god bless you, but god help you.])
Step three: describe some more. Look for the in-between things you missed. That broken nose wasn’t always broken, and you’ve described the nose now and how the nose used to be and maybe even you remembered to describe how the nose got broke, but in between the breaking itself and the current-day state there was another stage, a healing stage, a getting-used-to-it stage. Look for the gaps and fill them in. Stuff happens between lunch and dinner, often even food-related things. There is always more to say, more to tell.
Step four: consider plot once in a while. I don’t think a person really ought to worry to much about deciding on a plot ahead of time. Most plots can be summarized in two sentences. A guy moves in next to Gatsby, there are some parties, a reunion of long-losts, and the inevitable jealousy plus an accident result in a dead Mr. Gatsby. Poof, plot summary. When plot is necessary, plot will come. You don’t even really have to look for it. When you reach a certain level of description, like a maximum sustainable yield, a new field will be required of you in which to sew your seed, and at this moment a plot event will occur.
Step five: in this fashion, write more words then you ever thought your fingers could produce.
Step six: organize according to some principle or another, whatever your favorite thematic elements are that you keep stumbling across. Organize it like a good sentence, saving the most affecting moments for the end, or damn near it.
Step seven: cut the chaff.
Step eight: cut out everything else you can possibly cut, and remember reorganizing can allow you to cut some more.
Step nine: Go through every line and every word to reconsider voice and diction choices.
Revisit steps 7-9 sequentially as many times as necessary, depending on whether you consider your novel “good enough” to show to other people. If what you have left after any given step 9 is not something you would even consider to be a novel, you may have to revisit step 5 to add more raw material to the pile. Because ultimately, writing a novel is more a work of sculpture than it is a painting, and your job will be to chip, chip, chip away at the block until whatever it is you think might be inside it appears in its sharpest relief.
Step ten (David Foster Wallace only): minimize page length by taking any semi-extraneous or clarifying language and sticking it in the back as a smaller-font footnote.