Money is tied to self-esteem, and so asking for more money can be a challenge to your self-worth. Margaret Steen explains at Monster how to approach it at a new or current job.
The Search for Value
If it is a current boss, broach the discussion by saying you have evaluated your own performance and have taken into consideration what your boss has said about your performance, and you would like to talk about increasing salary based upon that. If the boss cannot or will not entertain raising your salary, then ask what the boss would recommend you could do to further increase your performance and value in the company. When dealing with a new job, express overtly how enthusiastic you are for the new position before explaining that you need more money to make it worth your while. If they do not offer you more money, inquire about potential future raises and incentives that might encourage you.
You can view the full article here: http://career-advice.monster.com/salary-benefits/negotiation-tips/the-right-words-how-to-ask-for-more-money-hot-jobs/article.aspx