1. you lead for 1/2 the pot he calls?
- I would think he's on a draw or has hit a piece. Value bet the river but outbet the draw possibility.

2. You pot it again and he calls?
- Same as above except consider a stronger holding. You are probably loosing at this point by two-pair or a set. It may be though that he has hit the same TP as yourself.

3. You check, he checks
- Value bet the river. regardless of what the 5th street is.

4. You check, he bets 1/2 the pot
- Double his bet. Take over the betting and lead out on the river.

5. You check and he pots it.
- Call. Value bet the river and fold on any raise.