Getting rehired by a former employer has more to do with your relationship with the old firm than it does your skills. If you can remain on good terms with the ex-boss, you're already on your way to regaining -- or even improving upon -- the job you left.
Be honest with yourself -- did you get along with your boss? The first step when leaving any job is to make sure you leave on a positive note whenever possible. Stephen Viscusi, author of "Bulletproof Your Job," says a company would want to rehire an employee for many reasons, but, almost without exception, when the relationship was good. Most companies really do like to hire back people who left on good terms because former employees already have the requisite experience, Viscusi points out. If the relationship was good and you feel comfortable, make the call.
Make sure your resume is updated and positively represents your skills, experience and education. This is your self-promotional tool, so make sure it reflects you in the best light -- but do not embellish. Start emailing your resume to your network of sources, making them (including human resources) keenly aware of your desire to come back to the firm. Ask HR to inform you of any open positions.
Go back and eat crow. This is what you must do to win your boss -- and the job -- back. As Viscusi points out, you fired your boss when you left him for Company B. His ego will need some massaging. Do not be afraid to tell him how much you missed the company and working for him.
Network with your former co-workers. Take advantage of these relationships and capitalize on the fact that they know your strengths and that they are insiders. Make a list of everyone with whom you worked or knew at your previous company so you see your company network laid out on paper.
Move back in, if the coast is clear. If your job ended on a sour note, which could have been due to difficulties with your manager, find out whether that person has left the company.
A lot of people don’t think to look at their old company, but good, quality people are always in demand -- especially trained, experienced former employees. If someone stole you away from the company and you come back, hoping to be rehired, that's very flattering. Don't be afraid to remind your ex-boss how much greener it was in her pasture. Have an answer for why you left and why you want to go back to your old company. Remain positive; rebuilding the relationships you left behind can take much more than a lunch or two.
Make sure you're not trying to be rehired by a boss with whom you did not get along. If you significantly damaged your reputation and or breeched your contractual obligations with your former company, don't even think about going back. It's a no-brainer when it comes to issues such as workplace violence and, to a lesser extent, lying on resumes and failing drug tests.