In addition to the Fiverr.com, elance.com and getafreelancer.com answers, I found my clients through the papers. I enjoyed a 4 year relationship with one client based in Johor Bahru while I was either in KL, or somewhere in Sarawak. By now, you could probably find such offers on jobsdb.com, & jobstreet.com.
Another way is to directly contact the client you are aiming. Send samples of your work.
By the way, what form of freelance writing work are you looking for? Creative, copy or technical?