just another note in regards to Social Signals:
I highly recommend the following networks for use in Socialization:
- Facebook (like & share)
- Digg
- StumbleUpon
- Kristi
- LinkedIn (if business related otherwise do NOT use)
- Google +1
- Yahoo Buzz
The usage of social buttons on-page is an influencer as well – metrics are measured and weighed with interaction.
Also, do NOT forget user comments and bounce rates – if you can induce a click beyond the page the signal may have additional weight