Make brief eye contact and smile directly at your target. Think about loving the world, or other people or a song that inspires you when you smile at people to be sure you project “joy” rather than creepy. If your target is inclined to be friendly they may well take control at that point and start a conversation. I make conversation with shy people who smile at me and look friendly all the time. Things like stuttering, awkwardness are all fine as long as you look friendly and receptive and appear to be listening. If eye contact is too intense for you nodding your head at points you agree with and briefly looking up interestedly works well for encouraging someone who is speaking to you. If you can keep yourself from feeling overwhelmed by avoiding those things that make you feel most awkward you will have more brainpower left to listen to what you are told, remember, and perhaps even venture a question or comment.