Determine whether or not you have been the victim of wrongful termination. Examples of an illegal discharge include violation of federal discrimination laws, violation of First Amendment rights, violation of a specific contract between you and your employer, violation of the company's own written termination policy, violation of a union contract and a termination because an employee refused to break the law.
Decide if your wrongful termination was the result of retaliation from your employer for taking any action protected by the law. These actions include taking leave under the Family and Medical Leave Act, serving in military reserves, participating in jury duty, engaging in activities that are legally protected by your union and whistle blowing, or exposing any unlawful practices by your employer to the authorities.
Investigate your state's at-will employment laws before you decide to sue for wrongful termination. At-will employment refers to the ability of a company to terminate employment at any time and for any reason--and an employee's right to quit the job under the same standards. While every state uses at-will employment policies in some shape or form, the degree to which these standards are implemented can vary.
Consult with a lawyer or legal professional to determine if you are the victim of wrongful termination, and decide if you should sue your former employer. Try to bring as much physical documentation as you can, including copies of any written contract you may have had with your former employer, copies of disciplinary action against you and even signed statements by other employees who witnessed your wrongful termination.
Follow your lawyer's advice to the letter once you have decided to sue your former employer for wrongful termination. Avoid trying to make contact with your former employer without the knowledge of your lawyer, especially in reference to the legal actions you are taking.