In addition to all of the above clues; If you can still find any generic /dictionary word of two, three, four, five, six, seven, eight and nine letters word, two words are also good if they are from good niche of say health, fitness, insurance, mortgage, mesothelioma etc and keyword with good searches of say 1000 and should also consider those with low competition and the CPC should be around $1 among those niches are good.
However, make sure you are buying the .com as a beginner, make sure the domain you are buying are those you can develop incase you don't have buyer on time.
Cheers.