I like overbetting for value against a particular type of player, one who doesn't have a good understanding of pot odds. Even players who understand that they need certain odds to draw to flush on the turn or something don't always understand the way pot odds function on the river. They don't get that if the pot is 150, they have to be right at least two out of every three times to call a bet of 300.

Instead, they base their decision solely or primarily on whether or not they think you have the goods. This means that this guy will either convince himself you have a big spade and fold to even a bet of 100, or he will decide you are stealing and call whether you bet 100 or 300 (though maybe not if you do something crazy like move all-in).

I've started taking notes on river calling standards: have I seen this guy fold to a blatant value bet? Have I seen him call an overbet with top pair when the flush hits on the river?

It can also be helpful to see how he value bets the river. Does he like to push the nuts or peddle them? He'll probably expect you to do the same, so if he always makes a very callable bet with a big hand on the river, he may get suspicious and decide you are stealing when you overbet, since he doesn't think that is the way to play the nuts. Conversely, he may may check-fold to a small bet when a scare card comes on the river, since that is how he expects you to play the nuts.