The most effective way to leave a job is by first ensuring your next move, if at all possible, then telling your manager in a professional manner, preferably face, to, face or through a formal meeting. You should give a proper notice (generally two weeks), write a brief resignation letter, and keep up your work ethic until your last day. You should also refrain from burning bridges, stay courteous, and maintain professionalism because you might require references at some point in the future.