1. Don't go crazy with the deductions. Business meals three times a day, five days a week is a red flag. So is writing off your family trip to Hawaii as a "research" trip (unless you actually are writing something about Hawaii). The crazier you get with the deductions, the higher the likelihood of being audited. There's a huge difference between writing off a couple hundred bucks a year in miscellaneous work-specific expenses versus writing off tens of thousands of dollars that could also be for the benefit of yourself and/or your family personally.

2. At some point you should be reporting a profit. It's understood that writing is a hit-or-miss industry and some years will be in the red. But if you're consistently writing off $5,000+ dollars of deductions and never making more than $50 in royalties, the IRS might decide to take a closer look at your deductions (i.e., audit). Again, there's a huge difference between writing off $5,000 in expenses and having a $10,000 writing income year, followed by a zero year, followed by another zero year, followed by a $4,500 writing income year than there is writing off $5K a year and never having anything other than a negligible income to show for it.

3. Keep excellent records. Make sure every dollar you're writing off is accounted for and that you can justify it. If you ever do get audited, you want to be able to provide the IRS with meticulous records that show them exactly how you arrived at the amounts you're deducting. If you wrote off $5,200 in expenses, you should be able to show them (with receipts) that it was $100 for paper, $1,000 for a manuscript edit, $500 for a book cover design, $985 to attend a writing conference, etc. Be precise in reasoning and your bookkeeping.