Keep tax records up to date. Save receipts in a folder, binder, or large envelope. Divide your receipts by the month, and then by the calendar quarter.
Deposit payroll taxes correctly and timely. IRS will assess penalties for failure to deposit, failure to pay, and failure to file, as well as assess interest. Use a payroll service, of you can not timely and correctly make federal tax deposits.
Don't mingle your business and personal checking accounts. All business expenses should be paid by a business credit card, by cash (get a receipt), or a business check.
Keep a travel diary for all business mileage. IRS Auditors deny the majority of business mileage, unless there is meticulous documentation. The mileage deduction for 2015 is 57.5 cents per mile
Sign your IRS personal and business tax returns, under "penalty of perjury".
Please call me at 702-589-7557, for small business IRS problem resolution.