Genre: It's tempting to think - I'll write my novel, leave categorization to others: it will be what it will be. This may be creatively liberating, compromising none of those artistic sensibilities, but there are rules worth considering depending on the style of the novel. Breaking them in a first novel is risky. Hideous as it sounds, half an eye (certainly no more) should be kept on who is going to publish, market and read it. You should also be familiar with your genre and trends within it. It's fine to discard such notions, immersing yourself in the frisson of creativity; but if it's been done before, better, or if such fiction is anachronistic / unfashionable, the words are unlikely to see the light of day.
Voice: Who's story is this? How are they going to tell it? Is their narration reliable? First- or third-person? If people are going to follow this person/s through 300+ pages, the voice needs to be convincing, compelling and original.
Research: Never skimp on getting it right. The worlds created may be fictional, but characters must still resonate, remind us of people we know or have met. Someone, somewhere will know that detail that seemed insignificant at the time. Most people are happy to give some time to answer a few questions, especially if they will be acknowledged. Don't guess how someone might feel or behave or think. Don't just Google the intricacies of bee-keeping - make friends with someone who does it.
Editing: Everyone works differently. Some surge on, amassing chapters of chaotic prose, revising only once finished. Others (myself included) prefer to edit yesterday's words before continuing. Try different methods, find what works best. How are you most productive? And realise this process is (almost) endless. One of the greatest assets is a dissatisfaction with your work. It should never be good enough.
Word count: All the writers I know set daily or weekly (minimum) targets. These can be modest (1,000 words a day) or more ambitious, but they are crucial. Firstly, however bad a day you feel you're having (there will be many), you will still have 1,000 words to show the next day to revise. Secondly, if you can stick to this commitment, you will have some idea how long the novel will take to write, allowing a glimpse at the finishing post. Thirdly, writing needs to be habitual. You need to be able to work regardless of mood, levels of inspiration or that thing what gets in the way: life. Think craft not art.
Right, did I pack those crampons?