Domain names should be as short as possible
example: www.mtn.co.za

Include your company name
example: www.absa.co.za

Domain names should be easy to remember or guess
example: www.telkom.co.za

Be easy to understand correct.
for example domain names like manny.co.za might be heard as mannie.co.za or even many.co.za! 

Include important keywords
example www.steel-engineering.co.za. Some search engines give better listings to sites that include important keywords in their domain names. Think of keywords that people might search for when looking for what you have to offer