OK, collecting all of that information was the hard part. Now it's time to figure out which percentage table to use. Again, not difficult — just reference "Appendix A" of IRS Publication 946. Plug in your system, method, recovery period, convention and so forth, and the chart will tell you which table to use, from A-1 to A-20.
The tables themselves are remarkable easy to use. There are vertical columns for each property class (3-year, 5-year, etc.) and horizontal rows for each year of the recovery period. Choose the class and recovery year and you'll find the percentage of the property's basis (cost) that you can deduct for that year.
Of course, if all of this talk of tables and conventions seems a little overwhelming, you can always use tax preparation software to run all of the numbers for you. Just don't overlook the potential tax savings of depreciation if you run a small business.
For lots more information about tax deductions and running a successful small business, check out the related HowStuffWorks articles on the next page.