How to select a Drupal development company
Knowledge in Drupal CMS:
Knowledge in Drupal CMS is a essential part. None of the company can develop better product without having specific skills. You should check the company Drupal skill-set.
Expertise and specialized in Drupal CMS:
Expertise and specialization is another part of choosing best Drupal Development Company. While doing Google search you might get many companies name list on top of the page that doesn't mean they are expertise and specialized in Drupal. Might they have done good job in SEO so that they came on top.