Hang around the right community... google by your thing.
By community I don't mean the social net but the group IN the social net.
Like groups in facebook.
Join the one that let you share video easily. In this case you're right to choose Youtube.
Join in... and share your video but share wisely.
This is where picking the community that inline with your interest is important.
Flow with what the community is tune in at the moment. Participate sincerely. Share within the context of the community's activity.
Never EVER spam.
No matter how good or important your video is.