Rates are set by fiscal year, effective October 1 each year. Find current rates in the continental United States ("CONUS Rates").
If you're an S corporation shareholder and work in the business, you are classified as an employee of the corporation (shareholder/employee) and treated the same way any non-shareholder employee is treated for income tax withholding purposes.
As an employee, your salary is subject to social security and Medicare taxes (FICA taxes). However, S corporation net profit is not subject to social security and Medicare taxes.
Therefore, if you pay yourself the lowest possible (and reasonable) salary, you would minimize your FICA tax obligation. S corporation net profit could be taken out of the business as a distribution by cutting a check to yourself. The net profit, whether distributed or undistributed, is subject to federal income taxes.
Make sure the salary you pay yourself is reasonable for the type of work you're doing. If the IRS deems your salary to be unreasonably low, part of your distributed (or undistributed) net profit could be reclassified as wages and be subject to employment taxes, plus interest and penalties.