Lose a good job and might not immediately get another to take its place. If you're fired, you could end up searching for months or even years before getting back to your present career level. If you are in danger of being fired, present solutions and use your persuasive skills to encourage your boss to reconsider.
Listen to your boss during performance reviews and during convesations about your work, attitude, attendance and interpersonal skills. Show that you are paying attention by nodding and agreeing when appropriate. Validate his concerns and point to your solutions for the problem. Agree to reasonable requests such as working longer hours or taking on additional projects -- as long as the request is ethical and legal.
Prepare for your meeting. Arm yourself with solutions. Be specific, point out how you will tackle issues in the future if you stay on the job. Ask your boss for his solutions. If he previously provided solutions, bring these along with your comments or point out how you've integrated them into your presentation. Reiterate that you recognize the seriousness of the situation and that you are willing to apply yourself wholeheartedly towards its resolution. Speak in a calm, even tone.
Explain any extenuating circumstances to your boss.Make him aware of personal problems that led to your poor performance. Point out the steps you've taken to deal with those issues or note that the situation is being dealt with to minimize the impact on your work. Explain that your performance will be at a satisfactory level if you are allowed to keep your job.
Suggest a transfer to another position or department if you believe you would be a better fit elsewhere. Research the position or department before your meeting and arm yourself with information that shows how this would be a good solution. Base your case for a transfer on logic and the benefits to the company.
Deal with small issues before they become bigger ones. Discuss work issues with your boss before they snowball into a bad performance review.
Sometimes, no matter how hard you try to convince your boss not to fire you, it still happens. Resist the urge to say something that you will later regret. Thank him for his time with grace and dignity, and he will be more likely to remember you fondly later in your career when you may need his help.