For most people, breaking the ice is the hardest part in starting a conversation with someone you don't know but after the ice is broken, everything esle should come easier.

To start, make eye contact, smile, and make a greeting, such as, "Hi, how are you?"

You: I'm Susan, what's your name?
Stranger: I'm Jack.
You: It's nice to meet you Jack. (If appropriate, this is where you would reach your hand out to shake their hand.)

Start with small talk by bringing up a topic that both of you have in common. This can be based on your immediate surroundings or the event you are attending, such as commenting on the music playing in the background or asking how they know the host. You could also talk about general topics such as the weather, current events, hobbies, school or work.

Keep the conversation going by listening to what they have to say and respond appropriately. Try to pick up cues on their areas of interest and expand on that. Follow up with additional questions and if the conversation starts to die out, don't be afraid to go in to other topics.

Tell them it was a pleasure meeting them. If appropriate ask them for their contact info.