By word score (descending), then alphabetically.
By word length, then by score (descending), then alphabetically.
By probability for you to win (descending), then by score (descending), then alphabetically
Hard words scoring assumptions
Opponent picks letters randomly.
Opponent tries vowels in sequence: a,e,i,o,u (skipping the free vowel) until first correctly
guessed, then continue randomly.
Each time opponent tries the letter that is most likely to be there (like our smart
frequency tool suggest on the right side of this page).