Losing your job isn't only embarrassing — it can be confusing as well if you don't understand why you were terminated. If you're at a loss about the loss of your job, take steps to understand the decision and to try and get your job back, if possible. Although you may feel anger and resentment, if you truly want your job back, it's important to express gratitude and humility. Writing a polite letter asking to be reinstated is a good first step. It also helps in your filing for back pay.
Write the letter in standard business format, including your contact information at the top and the contact information of your former employer.
Direct the letter to the head of human resources and copy the CEO or president of the company.
List your contributions to the company in your letter, along with the reasons why you believe you should be reinstated and solutions you've come up with to correct mistakes you made.
Avoid threatening legal or union action in this letter. This is a letter trying to get your job reinstated — using threatening language doesn't help you at this stage.
Show your desire to get your job back and do well at it. Offer reasons why a second chance might be warranted, and what you would do with that second chance if you received it.
Mail the letter with a return receipt requested and keep a copy for yourself. This way, if you do have to escalate to legal action, you have proof of the letter being both sent and received.