The value target
Dara O'Kearney shares a useful heuristic to encourage you to thin value bet more - the value target.

One big leak I see amateur players make is to not value bet enough, opting to check back hands that are ahead of a lot of holdings. The definition of a value bet is a bet which is ahead of more than 50% of the hands that would call. If you bet $100 on the river you do not have to be ahead 100% of the time for it to be profitable, you only have to be ahead more than 50% of the time.
Recreational players will often only value bet when they are 100% certain they are ahead, when in actuality they should bet when they are ahead more than 50% of the time. It’s not quite as simple as that sounds, you also have to factor in the likelihood of being check/raised as a bluff - if that is a possibility you should tighten your value betting range to adjust. How much you should tighten depends on how likely you think your opponent is to raise as a bluff. Against someone who is very likely to check raise bluff (which will force you to sometimes fold the best hand after betting for thin value), you might want to only bet hands that are ahead of 55% of the calls, whereas against someone who simply never does this play, you only have to be good 50.01% of the time when called.
Whatever the true percentage is, you leave yourself very open to exploitation if you do not value bet thin enough. When you only value bet monsters, your opponents will never pay them off. You need to be caught bluffing and value betting thin from time to time to get your big hands paid off. Not to mention you are missing out on a lot of value when your thin value bet would get bluff caught by worse.
The value target

My good friend and fellow poker author Andrew Brokos has a useful concept that should help you widen your value betting range, which he calls the Value Target. Think about the weakest hand you think your opponent would call with. Now think of all the hands above that hand that would also call, the halfway point is your Value Target, the hand your value bets have to beat. The Value Target is a useful concept for getting started at US online poker sites.
So let’s imagine the flop is 2-7-J rainbow and you think the weakest hand your opponent would call a bet with is 89s for a gutshow draw and A7s for middle pair. Think about all the other hands he would call with, you only have to beat the halfway point.
They would therefore call with 89s, A7s, 88, 99, TT, JT, QJ, KJ, AJ, QQ, KK, AA, 22, 77 and JJ.
The halfway point based on hand strength is therefore KJ, so that is where you can start value betting. Your value bets only need to beat KJ, they don’t have to beat Aces to be profitable. So your value bets are KJ, AJ, QQ, KK, AA, 22, 77 and JJ.
The whole process gets complicated by other factors, most notably blockers. QQ is a much better value bet than AJ, even though they are essentially the same hand, because the QQ unblocks hands like A7s in the villain’s calling range. 22 is a better value bet than JJ because it doesn’t block JT/QJ/KJ/AJ.
Also you have to factor the bigger hands and bluffs reraising you.
However, it is a very useful concept to get started with if you know you should be betting thinner for value. Identify the halfway point in the Villain’s calling range and remember that you don’t have to beat all their hands, just more than 50% of them to be profitable.
Dara O'Kearney's book Endgame Poker Strategy: The ICM Book is out now.