One of the most important things you can do as a freelance writer (whether you work predominantly online or off) is networking with other writers. Many of the best freelance writing gigs are never published, but can be passed along by writers in your network who have come across it through their contacts. A strong network can also lead to referrals.
All writers will occasionally come across gig offers that don't fit into their schedule, their rates, or their niche. By keeping a strong network, they can point that client to another quality writer (hopefully you).
Join freelance writing forums that allow you to advertise your services where other writers can see your rates and specialties (like our AllFreelancing.com freelance writing forum).
Join small networking groups or even professional organizations dedicated to freelance writers or professionals in your niche.
No matter how you do it, just get started! The longer you wait before starting to network, the more job leads and referrals you're missing!