If you feel uncomfortable approaching a stranger, that's okay. Many people feel shy about this. If someone makes conversation with you, focus the conversation on him or her. Ask questions about their life, and keep them talking until you find common ground. Place all of your focus on the person you're sharing a conversation with. Really listen to what they're saying. If your energy is focused away from how you feel, you'll be less likely to be overtaken with the feelings of shyness.
Attend the gathering with your significant other or a close friend. You're more likely to meet people if you have mutual friends.
When making small talk, ensure that your questions are about less personal topics. It's okay to ask someone whether they're married or have children. Stay clear of asking for details about their divorce or custody battle.
It may also help you to encourage the other person to do more of the talking. Use open-ended questions where they can launch into a whole story or explanation instead of just answering yes or no questions.