Understand the basic law of overtime compensation. Overtime law is governed by the Fair Labor Standards Act. Under the Act, employers must pay overtime at the rate of one and one half times their regular rate of pay to all eligible employees working more than 40 hours per week.
Realize that only "non-exempt" employees are entitled to overtime. Non-exempt employees are those that do not fall within the categories of executive, administrative, professional, outside sales or computer employees as defined by the Fair Labor Standards Act.
Gather information. Before you sue for unpaid overtime, get copies of all papers that relate to your claim. These can include time sheets, payroll records, your employment agreement, correspondence between you and your employer, employment policies and procedures, etc. Make a list of any and all witnesses to your claim.
Consult an attorney experienced in overtime pay issues if you have any questions at all regarding your eligibility for overtime compensation, and for advice and representation regarding how to sue for unpaid overtime.
Contact the Department of Labor which can investigate unpaid overtime claims. You can request a complaint form from the department or go there in person to speak with an investigator. After receiving your complaint, the department will review your allegations and assign an investigator to talk with you, your employer and any witnesses before issuing a decision.
File a complaint in state court. With the help of your attorney, prepare a complaint against your employer for violation of the overtime laws and request an award of all money damages resulting from the violation. If you win, you may be entitled to recover twice the amount of overtime owed to you, litigation expenses and your attorney's fees. File the complaint in the appropriate state court in your jurisdiction.