There is a very simple way to do this, as twitter and fb are happy for it

1) Login in your facebook and twitter accounts, keep logged in

2) http://www.facebook.com/twitter/   – Type this on your facebook URL

3) If you have pages in your fb account, it will show you all the pages, and ask you which page you want to link with your twitter account.

4) Select the page and tht’s it.

5) Now whatever you write on your fan page, reaches your twitter automatically

Njoy !!