As a host and hostess you have to be careful that everyone has a good time. Introducing people is an art and for your party, you got to do it right.

Introduce the people who seem to be shy to those who will talk. Ask anyone who seems to be alone a lot through the evening, if they have been introduced.

Mingle, Mingle and Mingle!
Introducing newcomers as they come in is the simplest way.If you know that some people may have similar interests but do not know each other, make sure they are brought together.
Make sure everyone has their first drink, knows how to serve themselves after, and then let everyone including yourself mingle.

Points of Interest
When you introduce people to each other, briefly mention some points of interest about each person so they have something to begin talking about.

Rules:
Introduce individuals to each other using both first and last names. 
If you’re introducing someone who has a title ‘a doctor, for example’ include it. 
Introduce the younger or less prominent person to the older or more prominent person, regardless of the sex of the individuals. 
If the person you are introducing has a specific relationship to you, add a phrase like ‘my boss,’ ‘my wife’ or ‘my uncle.’
For unmarried couples living together, use the phrase ‘companion’ or ‘partner’.  
Use your spouse’s first and last name if he or she has a different last name than you. Include the phrase ‘my wife’ or ‘my husband.’ 
Introduce the group to the individual first, then the individual to the group.

Tips & Warnings
If you’ve forgotten a name, it’s less awkward (and better manners) to apologize and acknowledge that the name has escaped you.