how to get more and better contribute in github?

I have use github for a while, but my project is only one developer -- myself.

I want to get some contribute from others, and some of my friends said they can give me some patch, but we all don't know how to use github as a tool for us.

And I know that github will also help project get more contribute from the open source community.

So, my question is

1. how to get contribute in github?
2. how to get more and better contribute from opensource community?