All the cards have been dealt, and all the bets have been made. Now it's time to show your cards. And if you have the best hand, you will win, and if you don't, you will lose. Now, it may seem that this is all we have to or even can say about this part of the game. This isn't exactly the case though.
First off, in general, people tend to show down their cards too much. It's not that the showdown itself costs you any money, but in almost all cases, the process of getting there has cost you anywhere from a decent amount to plenty to have the privilege to see if your hand is best. So the showdown in this sense is a reflection of what has transpired earlier in the hand.
This tendency to frequently see showdowns arises from not only too loose play, but a desire for action, and also a desire to win money. It is important that we seek to curb both desires, beyond the extent that it would be profitable to stay in the hand. Much the same way as wanting action and wanting to win pots may tempt us to play more hands pre-flop than we should, these desires also can have us playing on past the point where it would be a good idea.
And post flop, we now have the added psychological problem of being pot committed, where the more money you throw into the pot, the more difficult it seems to be to get away from the hand. It is a bad idea though to throw good money after bad, and we must always see money previously invested in the pot as no longer ours, and see each decision to contribute more money to it or not as independent of any previous contributions. Otherwise, our thinking is going to be distorted, as how much we have previously invested in the hand has absolutely nothing to do with our current chances.
Another way people can tend to go wrong is by assessing their strength of hand in terms of being the present best hand, instead of the likelihood of it winning the hand. And the two are not the same thing. A good example of this is betting a low top pair on the flop with several callers. Yeah, it might be the best hand now, but the chances it will be the best hand at the turn aren't very good, as the card that falls is likely to hit someone else's hand, and put your junky pair behind. And the chances of it winning at showdown are even less, which is what we need to be concerned about.
Of course, winning at showdown isn't the only way to win the hand. You can take the pot down of course. You always need to think in terms of your chances of winning though, regardless of the means you win by. In a loose game, especially where people tend to call you down a lot, your chances of winning at showdown is going to be an element of your game that you need to pay a lot of attention to.
So to bring the thing together, players tend to go to showdown too many times, mostly because they haven't assessed their chances of winning at showdown properly, and thus lose at showdown too much, both in terms of percentage of times going to showdown, and the number of losses.
Most players, in fact, lose more times than they win at showdown, in addition to going there too many times. And the two are very strongly related. Some players who profess to be knowlegable will tell you that you should average about a 50% showdown win rate. This is too low, and we'll look at why this is the case.
Let's look at two players, one which wins at showdown 50% of the time, and one that wins 70% of the time. Now, the player who wins the 70% is going to show down less hands of course, by being more selective. Let's say he shows down about half the hands of the other player, which is pretty typical. So, in 10 hands, he wins 7. The other player wins 10 of 20. So, in the additional 10 hands he played which the opponent didn't, he only won 3 and lost 7. And that's not a percentage that's acceptable by any standard. So our hero, by not getting involved in these 10 additional hands, is saving himself money, since the 10 he plays are profitable (7 wins 3 losses), and the 10 he doesn't get involved are a losing proposition (3 wins 7 losses). Not to mention having a lower variance, which is desirable as well.
These numbers are readily accessible if you have Poker Tracker or a similar software package, which tracks this for you. You wouldn't believe how many players who are profitable crow about having this in the low to mid 50's. They cite the fact that they make this or that amount of bets per hour as evidence that this works. What they don't grasp though is that there are more profitable players, making more money per hour, with a significantly higher win rate at showdown. And this is manifested by the fewer mistakes a more selective strategy produces.
All this is not to say that you don't want to call at the river if you don't have over a 50% chance to win the hand. You need to look at things like pot odds for that. What makes showdown percentage significant though is that it brings together your play over the entire spectrum of the hand, and shows what sort of cards you will play to the end.
If you typically play in ridiculously loose limit games where there's usually a whole bunch of people showing down every hand, or in a very passive game where everyone tends to check way too much, then perhaps 50% or so is going to be enough, and perhaps even ideal. However, in the overwhelming majority of games, things won't be this far off the norm to make that a desirable result.
So what should the percentage actually be? Well, it depends a lot on the type of game. The elements here are: how much is it going to cost you to show down, and how important is it to win the showdowns. In limit poker, for instance, you can get by on a lower percentage - 60% to 65% is good. At no limit, you want it to be higher than this - 70% + preferably, since it costs you more if you are wrong. And in a tournament, it needs to be higher again. Make a habit of losing showdowns at a tournament and you'll soon be watching from the rail.
So, showdown win percentage is an important and effective diagnostic tool as far as evaluating your game is concerned. It will tell you anything from the fact you're playing too many cards pre-flop, you're calling too many raises both pre and post flop, you're seeing too many turns, you're seeing too many rivers, and/or you're calling at the river too much.
In a nutshell though, a too low win percentage at showdown can be reduced to one simple thing - you need to fold more. And you need to fold to the point where this percentage becomes more ideal. Where you're going to need to fold is something that can only be discovered after looking at each aspect of your game. However, by solving this problem and getting your percentage into a more preferred area, you will add considerable profit to your game, regardless of the type of game you play.