Well, you can't be absolutely certain you won't get sued, no matter what you do. But there are steps you can take before you fire someone to make sure that you've considered all of the angles. For example, you should investigate the situation for which you're considering termination. You should review the employee's personnel file. And, you should run your decision by another manager -- or, in some situations, a lawyer -- before you carry it out. For more information on the steps to take before firing someone, see Nolo's article Should I Fire an Employee?