Network. Go to SM events, drink nights, etc. The more people know you the more work will come your way.
One thing I notice is 'young' stage managers want to work on Broadway right away. Well, when you play with the big boys you better know your stuff and I don't just mean the paperwork. If you have a hard time relating to older men (IA) or have a difficult time working with "stars" then wait. The one thing you don't wnat to be is a one show wonder. Several stge managers from outside NY come in and work on Broadway and without knowing it, make enemies and never do another Broadway show again.
Pay your dues on the road and then come in.