If you don't have contacts then make contacts. If you don't have anything to show, then make something to show.
If you are a developer/designer, here are some suggestions:
1. Don't leave your existing job unless you have enough money in bank to sustain for a year or two.
2. If you don't have projects to show in your portfolio, then do some projects. There are endless possibilities. You can make and sell themes(wordpress/shopify/etc), html templates, plugins, mobile apps, etc. You can also offer free development/design services to some startups in need[1]. You can take some existing popular website and redesign it for better UX.
3. Get your own website. Put your Projects/CV/Blog on it. Write blog posts related to your area of expertise. e.g., on UX design, how to do <something> with <xyz> language, etc.
4. Answer questions on sites like stackoverflow, quora, HN, reddit. Build your online reputation and contacts. Don't hesitate in sending mails and communicating with people you meet online. Ofcourse, don't spam.
5. Attend meetups. Not only technology meetups but any meetup that you can attend and possibly find clients.
6. Share your business card with people you meet. Tell them about what you do(freelancing). Ask them what they do. Think what you can do to make their life a bit easier.
7. Still if you don't have any projects, if possible, make small SAAS or Open Source products that can be of any use to someone.
It may take time. You need to toil hard. So have patience and keep working. :)
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[1] Here are some examples :
http://news.ycombinator.com/item?id=1842768 and its follow up : http://news.ycombinator.com/item?id=1860130
http://news.ycombinator.com/item?id=1838273
http://news.ycombinator.com/item?id=1838033
http://news.ycombinator.com/item?id=1836998