Can I upgrade from Drupal 7.10 directly to Drupal 7.12 Should I upgrade from 7.10  to 7.11 first, then upgrade from 7.11 to 7.12? 

Or can I just upgrade from 7.10 directly to Drupal 7.12?
You can update directly to 7.12 without any problems. Drupal 7.11 contains security fixes while 7.12 contains bug fixes. Updating to 7.12 would also add the security fixes from 7.11.