I started working freelance in 1996, so I have a few years under my belt. But I still learn new things about taxes every year. Here's a few tips, most of which you probably already know.
1. Take advantage of Section 179 deductions. The limits change every year, but this year it's basically no limit at all (over 100k). Any valid business equipment expense that you would have needed to depreciate over time, you can deduct as a straight-line expense. Computers, cell phones, COTS software, office furniture, and mixed-use equipment (stuff you use for the business part of the time, for personal use other times) all qualifies. Details:
http://www.section179.org/property_that_qualifies_for_section_179.html2. 50% of Meals/entertainment expenses. To qualify an expense must be "customary for your trade" and pass one of two tests; they're pretty easy to pass. For example, drinks with coworkers after work for networking purposes would probably qualify. Details here:
https://www.irs.gov/publications/p463/index.html3. Mileage to/from customer site. If you make your home your official work site, mileage to the office is deductible. You do not have to take the home office deduction to qualify.
4. Premiums for your health insurance are deductible on line 29 of the 1040 (probably an obvious one for you).
5. Wages paid to "helpers," which may include family members, are deductible as a business expense. Anything under $600 does not need to be reported on a 1099. Likewise any expenses for an accountant, lawyer, etc. are all deductible as straight line expenses.
6. Expenses under $25 do not need a receipt to qualify, in the event of an audit.
7. We cover this in the forum often, but SEP-IRA and Solo-K options are super awesome for contributing up to $53k a year in tax-free retirement savings.
I claimed $35k in non-wage business expenses last year. I kept each month's receipts to support this in its own folder, for audit defense. I plan to keep these for seven years.