A good domain is brandable
A brandable domain is non-generic. It’s the difference between a sticky-plaster and a band-aid. Unique is good, rare is acceptable, generic is a waste of money.
A good domain is flexible
Keep it flexible. Don’t tie yourself to one market or one demographic. Your domain name needs to work now and fifty years in the future.
A good domain is musical
Six to 12 characters and two to three syllables is the sweet spot. Names in that range have a musical rhythm our brains find it easier to retain and recall.
A good domain is phonetic
There are 44 word sounds in the English language. Other languages have similar totals. If you use a domain name that is pronounced phonetically, it will be easy to communicate.