Looking at the current board state:
```
 O | X | X
 -----------
 X | X | O
 -----------
 O | . | .
```

I need to decide between positions 2,1 (bottom middle) and 2,2 (bottom right).

By placing my O at 2,1:
1. I block a potential threat from my opponent - they currently have Xs at positions 0,1 and 1,1, and could win with a third X at 2,1.
2. I set up a potential winning move for myself in the bottom row - I'll have Os at 2,0 and 2,1, with 2,2 being the winning position.

While placing at 2,2 would also set up a potential win in the bottom row, the 2,1 move has the added benefit of blocking my opponent's vertical threat in the middle column. This gives me better control of the board and forces my opponent to defend rather than attack.