As a generalization, the money a business owner spends in a business becomes a tax deduction. So, while you don’t get to be crazy in your spending, anything that is ordinary and necessary, you can deduct.
However, there’s an exception to this general rule: Business deductions require you already have a business—and usually you start spending money before you start the business. Unfortunately, tax laws state that this “startup expenditure” spending which occurs before the business starts can’t simply
be immediately deducted. You have to use more complicated accounting which delays, minimizes or even eliminates your deductions.
The October 2011 issue of the Business Owners Tax Newsletter describes these rules for startup expenditures--and tricks for making sure you don't get beat up badly by the rules.