First work on your own site (or sites) so that you have something to show a potential client. It is going to be hard to sell your services if there is no proof that you have ever increased the traffic flow to a website, or increased its ranking in the SERPs... This shouldn't take that long - find a very small niche and rank a website with good information on it - then use that to show clients that you can rank for specific keywords, etc.
You can go on odesk.com and post the services you provide and people can hire you. You can also browse for seo project you might be interested to take on and aply for them.
Study, study and study.. this isnt easy job like many people think. Buy some sites, make then succesfull, create portfolio and promote it on internet. Offer you services here on DP or Odes, Elance, etc. Or directly contact companies in your country.
The thing is you should show that you are a skilled professional, if people won't know any evidence of your previous work then they would be doubtful to you. Well, for finding works, you can use this forum as well, in service section, it may help.
Just try participate in freelancing site and in social networking you will get best projects. At the same time Participate in forum posting regularly. SEO Projects you can get