river overbets and river bet sizing tells

[tagWAG]

Do you ever make river overbet bluffs?

I don't think I've ever bothered to plan a c/r bluff on the river (they seem to happen by accident when I was going to give up, but then villain bets a weird amount...), but there must be standard spots to watch out for when this is likely to be worth considering?

What sort of river bet sizing tells do you typically rely on?

For instance, assume we are h/u and ip on the turn with a decent but not great made hand. In limit there may be all types of reasons to raise for a free card or showdown. But in NL these types of plays aren't usually such a good idea, not least because our opponent's bet sizing on the river will give us new information about the strength of his hand that we don't need to pay for on the turn. What are your favorite river bet sizing clues?