Facebook and Twiter is under social media category in terms of SEO which mean you can get instant traffic. You can create fan pages on facebook and accumulate likes and on twitter just build your account and get thousands of followers, tweet frequently with offer and not to look your account legit.
just create facebook fan page and start your posting with your facebook friends and other social networking website..but remember that don't posting again and again same link posting..only post useful and informative contain and ask questions...
use Fan page and describe in details about your products or company and share some posts about yours...