• Overall, you should shop around to find a registrar that provides the service or range of services you need.
• Get competitive quotes - but remember, the cheapest price is not necessarily the best deal.  Check your contract for any 'hidden' charges.
• You should ask to see copies of the registrars’ Terms and Conditions for ENUM registration before making your selection.  If these are not easily available to you - usually via their web site - insist on having a copy sent to you and study it thoroughly.
• Seek recommendations from other ENUM users and ask the prospective registrar for testimonials from other customers.
• Check whether the registrar has signed up to an industry code of conduct.
• Consider whether you need any specialist services - not all registrars offer the same package.
• Research what is available from which registrar through the media.
• Pay particular attention to your rights to move your business and your ENUM registration to another registrar, and whether there is a charge for doing so.

Take a look at the list of Nominet accredited ENUM registrars.