As for yesterday's, I had the S in place, and the yellow letter I got was R, which I assumed would be the last letter. I'd eliminated A and E, so I knew there'd be at least one vowel in there out of the 3 remaining, possibly two. Then I started to think about letters that would go with S at the beginning of words, SH, SL, SP, etc, until I got to SC and imagined adding 2 vowels in there, and voila, SCOUR. But let's face it, most times you get it in less than 3 guesses there's a healthy amount of luck involved.