I believe there are courtesies we should abide by when we are at any social event. Whether we have a bunch of friends with us or not we should be nice and welcoming to any person who is alone and new to the group.
Here is a list of party manners:
1. Make eye contact with the person next to you, don't ignore them because that is rude.
(If you are shy and feel uncomfortable about this action, think about how uncomfortable you are making the person sitting by you feel. Get out of your own head and think about someone else.)
2. Engage in conversation with the person near to you. Even if it is the shallowest form of conversation, such as, "that was yummy!" Never say anything negative, stay light and cheerful.
3. When someone new comes into the room and it is clear that they are alone, go over and introduce yourself. This makes the newcomer feel more comfortable.
4. If you are in a circle of friends, a new person comes to the circle, step back to open the circle up, allow the newcomer in and introduce yourself.
5. Smile as often as you can and be open for conversation.
Here are opening questions to break the ice:
"Where do you live?"
"How do you know the host?"
These 2 questions can lead to some interesting conversation. Engage in the moment, smile and have fun.