Use your friend group to help you. In a situation with people you don't know, have one of your friends work with you and introduce topics into the conversation... asking your opinion on something, for example. Then you can begin the interaction by looking at and interacting with a person you already know well and feel comfortable with. Then that friend can engage a different person and bring them into the conversation and you can follow their interaction with your eyes on the stranger. Look at the person and nod or whatever when appropriate, even if they are not looking directly at you, and listen. If you relax and focus on what they are saying, while they are talking to (and looking at) your friend, you will likely become more comfortable talking to (and looking at) that new person. It's a place to start, anyway.