First, stop stating that you're shy and an imposition, etc. "As a man thinketh, so is he" so use the power of words/thought to create what you want, not what you don't. (google some affirmations to post around your house/repeat to yourself)
Second, remember that not everything is about you. Meaning that *they* want to be accepted just as much as you do.
Third, arm yourself with some tools (conversation starters, good jokes, funny story, etc).
Fourth, you may be the friend someone else is looking for so just be friendly and relax.
Last, smile and enjoy yourself.
Kudos for stepping out of your comfort zone.
Oh - genuine compliments and asking for ideas and opinions can go a long way.