The kind of distributor you choose will depend upon the size and extent of your enterprise.   A well-established label may be best served by partnering with one of the major-label distributors.  A small specialty label, on the other hand, will seek the services of one of the independent distributors, with expertise in the the label's style of music.
      Let's consider that you've been hand distributing to local stores and have had some success, some success not only in mom and pop shop sales but on gigs as well, with this in consideration, you should be ready to approach a distributor.   The reason for you to consider the latter is because when you do approach a distributor the main question is going to be, can this artist sell?  The main convincing of this fact is going to be in proven records.  Follow me?  To them it's all about potential success, so before you walk you must crawl.  \
   If you just starting out, consider working with an Internet-based distributor that supplies product to brick-and-mortar retailers as well as online megastores.