Be sure that your requests are reasonable and in line with the current marketplace. If the salary offer is below market value, gently suggest that it's in the company's best interests to pay the going rate. Be a confident negotiator. Part of convincing employers that you're worth a certain amount is convincing them that you believe you're worth that much. Use confident body language and speech patterns.
Silence is another important weapon in creating a confident image.
When you make a salary request, don't go on and on, stating over and over again why it's justified. Make your request and offer a short, simple explanation of why that amount is appropriate. After you state your request, be quiet. Let the employer win, too. It's a smart negotiating strategy to ask for a few benefits or perks you don't want that badly.