Someone with Narcissistic Personality disorder (NPD) has at least 5 of these symptoms:

has a grandiose sense of self-importance (e.g., exaggerates achievements and talents, expects to be recognized as superior without commensurate achievements)
is preoccupied with fantasies of unlimited success, power, brilliance, beauty, or ideal love
believes that he or she is "special" and unique and can only be understood by, or should associate with, other special or high-status people (or institutions)
requires excessive admiration
has a sense of entitlement, i.e., unreasonable expectations of especially favorable treatment or automatic compliance with his or her expectations
is interpersonally exploitative, i.e., takes advantage of others to achieve his or her own ends
lacks empathy: is unwilling to recognize or identify with the feelings and needs of others
is often envious of others or believes that others are envious of him or her
shows arrogant, haughty behaviors or attitudes

Here are some more signs of Narcissistic Personality Disorder to look out for:

Jealousy and possessiveness
Excessive need to feel special, adored, loved, appreciated, or admired
Rage attacks when you do not sufficiently meet his/her needs
Controlling behaviors (trying to control how you spend your time, who you talk to, how you dress, etc.)
Inflated self-esteem, or grandiosity (bragging, "fishing" for compliments)
Dramatic, insecure behaviors
Expecting you to take responsibility for making him/her feel better about him/herself
Blaming you for behaviors or feelings (i.e., "YOU made me do this," or "YOU made me feel this way.")
Not taking responsibility for angry behavior and justifying angry outbursts
An attitude that demonstrates "the world revolves around me" and "you need to cater to my ideas, opinions, thoughts, and feelings."
An unwillingness to reflect on his/her own behaviors