Are we talking parameters from an SEO standpoint, or Domaining standpoint?
If SEO, you would want to be looking at parameters like MOZrank, PageRank, DA/PA/TF. Some webmasters look for higher numbers than others, so it really depends on what you want. If a Domaining standpoint, you would want to find parameters like how many Google results a domain may have, are there any potential businesses with similar domains already developed, are there limited numbers of them (such as LLL/NNN..etc)
I'm not really sure about your second question because it doesn't make much sense to me.