The best way to do it, or the most reliably I’ve found, is described below. I’ve tried using my blog’s RSS feed in the raw and it works on a one-off, but for some reason facebook doesn’t retain it and the link breaks. In addition, the twitter plugins don’t reliably work over long periods. But at work we used Feedburner and it’s been working for a long time so it seems the best solution. Here’s how.
Set up a Feedburner feed for your blog at http://feedburner.google.com/
Now you want to add your feed to Twitter. This can be done from within Feedburner. Choose the Socialize option under the Publicize tab and add your Twitter account. You will be prompted to login to Twitter (if you aren’t already) and to confirm Feedburner’s access to your account.
Now for Facebook…
You will use your feedburner feed address e.g. http://feeds.feedburner.com/royhair as the RSS address for facebook.
So – log into Facebook and from the Home page access the Notes / My Notes link on the left of the page. Then choose to edit notes.
Add the Feedburner address for your feed and submit then confirm.