There is no question that Twitter and Facebook can drive a ton of traffic to your website. You will have to find a way to get your posts in front of the people active in those communities. Sharing your posts on Twitter and Facebook is a good start. WP-AutoSharePost is a handy little app that automatically sends your posts to Facebook and Twitter.
WP-AutoSharePost saves you time sharing your posts on Twitter and Facebook. It does it automatically. You do need your keys and app IDs from those sites to get this plugin to work. The script can also grab comments from Facebook. Bit.ly shortening for URLs is available as well. Keep in mind that you will need to use a real cron job to get the Comment Grabber feature to work.
WP-AutoSharePost is a time-saver of an app for anyone active on Twitter and Facebook. Just set it up and let it go to work for you.