The Holy Grail of strategic Scrabble play, a triple-triple (or "nine-timer," as it is called across the pond) is a word which covers two triple word score spaces in one turn. Consider:
a b c d e f g h i j k l m n o
-----------------------------
1|= ' = ' =|
2| - " " - |
3| - W I L D C A T s|
4|' - A - '|
5| - L - |
6| " " L " " |
7| ' ' O ' ' |
8|= ' P R A Y E D =|
9| ' ' ' ' |
10| " " " " |
11| - - |
12|' - ' - '|
13| - ' ' - |
14| - " " - |
15|= ' = ' =|
-----------------------------
The most recent play was WILDCATs 3H 30 (go look at this for how this notation works), leaving a wide-open S at O3. Bad move! Leaving a power tile like S between the two triple-word spaces creates a high-risk place for your opponent to play a high-scoring triple-triple, as we'll soon see:
a b c d e f g h i j k l m n o
-----------------------------
1|= ' = ' U|
2| - " " - N|
3| W I L D C A T s|
4|' - A - E|
5| - L - X|
6| " " L " " I|
7| ' ' O ' ' N|
8|= ' P R A Y E D G|
9| ' ' ' ' |
10| " " " " |
11| - - |
12|' - ' - '|
13| - ' ' - |
14| - " " - |
15|= ' = ' =|
-----------------------------
UNsEXING O1, (1+1+0+(1*2)+8+1+1+2)*(3*3) = 144, plus 50 for bingo = 194 points. Ouch.
Any time your opponent leaves the triple-triple lane open, before you play, double-check to see if you have any possible plays there; scores of over 150 are not uncommon for triple-triples, and the demoralizing effect that these high-scoring plays have on your opponent can be devastating. Contrariwise, if you make a play that opens a triple-triple lane, make damn sure that it's going to be worth it if your opponent comes down with QUIZzING for 258 points.