You should definitely add a link to your website in the description of the page. In the posts you can be adding links to different posts from your site, but don't over do it! Post other funny, interesting or inspirational stuff as well.
If you do it right, than Social Media is a gold mine of free traffic!
Good luck
Art

Posting in Facebook groups can be a good way of driving traffic to your website. However, obviously the groups you post on should be relevant to your niche and website. Its no good posting womens fashion content in an IM Facebook group.

Also you won't get much traffic from just posting links to your site telling people to visit. Best way is to post value in your group posts, explain what benefits the reader will get from visiting your site and reading the full post.

If you write blogs on your page, use those to drive traffic to your website from Facebook.

Well how long does it take to post your URL. 10 seconds perhaps? So you tell me. Is 10 seconds of effort worth getting even a couple new people to your site?

If you don't have your fan page or running ads directly with Facebook your conversion rate will suck.

In anything you do, your traffic must be targeted in order to truly benefit from your business.

The best way is to build an awesome fan page.

Instead of posting direct links to your site on other pages and groups, simply join those as your fan page. Contribute to the groups in a non-promotional way. You will get quality traffic this way.

Of course, that should only be one way of growing your FB audience. You should also consider FB advertising and promoting your page outside of FB.

Just don't spam, and you are good to go. Also you should consider adding YouTube, Twitter and Pinterest to your social portfolio.

Pin your posts on pinintrest and submit your posts on StumbleUpon and tumbler thats is very useful for increasing traffic on your website.

I am starting to have my doubts about Facebook. At least for younger demos.
Many younger visitors are leaving the site to go elsewhere.
Have been testing Pinterest and having some decent luck there.

Definitely post your link but remember that everyone's doing that. I like to find really great inspirational videos, quotes and images. Spread some genuine inspiration and people will be drawn to you. I remember a man that did nothing but post great quotes. He had a huge following because people felt good when they went to his page. Remember to unleash really great content, and like the gentleman said above, share the benefits of your content and you will go far! Good luck!