General guidelines
1) No hyphens
2) No numbers
3) Two words only
4) Should make sense
5) Address a huge market / strong niche market
6) use present tense
7) use verbs / adjectives/ nouns only
8) search marketleap, alexa , overture, google ratings
9) search for occurance of the word
10) see if other extensions are taken
11) trademarks
so on