"Bet more than your opponents can call profitably, but don't bet so much that you blow your opponents off their hands. Bet an amount that entices them to make a bad call." - NLHE Theory and Practice
What's the right amount on these rivers?

1.)
Party Poker No-Limit Hold'em, $ BB (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Button ($99.50)
SB ($216.58)
BB ($135.50)
UTG ($105.90)
UTG+1 ($106.30)
Hero ($269.25)
MP1 ($96.25)
MP2 ($98.50)
MP3 ($27)
CO ($188.69)

Preflop: Hero is UTG+2 with 7, 6. SB posts a blind of $0.50.
2 folds, Hero raises to $4, 3 folds, CO calls $4, 3 folds.

Flop: ($9.50) T, 2, 8 (2 players)
Hero bets $6, CO calls $6.

Turn: ($21.50) A (2 players)
Hero bets $14, CO calls $14.

River: ($49.50) 9 (2 players)
Hero bets $30, CO calls $30.

Final Pot: $109.50

2.)
Party Poker No-Limit Hold'em, $ Hero (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

MP2 ($100)
MP3 ($209.58)
CO ($125)
Button ($159.25)
SB ($100.80)
Hero ($305.25)
UTG ($98.85)
UTG+1 ($128.40)
UTG+2 ($28.50)
MP1 ($21.50)

Preflop: Hero is BB with A, 5. SB posts a blind of $0.50.
UTG raises to $4, 8 folds, Hero calls $3.

Flop: ($8.50) 3, 3, 4 (2 players)
Hero bets $6, UTG calls $6.

Turn: ($20.50) 2 (2 players)
Hero bets $15, UTG calls $15.

River: ($50.50) 7 (2 players)
Hero bets $40, UTG calls $40.

Final Pot: $130.50