You should have an effective 15 to 30 second pitch ready. Be prepared to introduce yourself and make your contact aware of what you can do for them in 30 seconds or less, because that may be all the time you have. You should be passionate, energetic and personable. Have a few introductions prepared that way you can use the appropriate one for any given situation.
You should not try to sell while networking. Networking is about meeting new people, making contacts, and building relationships, not sales pitches.