Make Every Play for a Reason

So many poker players make plays just for the sake of making them.
Don't let this be you.
With every play you make, you should have a clear view of what it is you want to accomplish.
The key to making good decisions is to have an outcome in mind. You should make every play for a reason.
So ask yourself what you're accomplishing before you make your play.

Never Not Know Why

I have a friend who "plays" poker; sometimes I rail him.
Whenever I see him make a questionable move I ask him, "Why did you do that?"
Often I'm met with replies like, "I don't know" or "Didn't really think about it" or "Just because."
This is not the way to play poker.
Just guessing at things and betting or checking for the sake of doing it is not playing poker.
Each decision you make could lead to winning or losing your stack, so you have to be sure to give each decision your full attention.
Whenever you act, you should have a goal.
Are you trying to make your opponent fold? Are you making a value bet?
You must clearly conceptualize the purpose of each action before you perform it.

Example 1

Game: $1/$2 No-Limit six-max; effective stacks $200.
You have A♠ J♣ in the big blind. It's folded to the button, who raises to $8.
The player on the button is a tight-aggressive player - stats-wise something like 19/16/3.
The small blind folds and you ... take some time to think about the situation.
Your options are three-betting, calling and folding - all of which are decent choices.
Some of course are better than others.
Because the button is raising a fairly wide range, you decide you're not going to fold your A-J.
Against a tight opponent, raising from early position and then folding is an easy play.
But the raiser from the button will be raising a huge range.
Since you're way ahead of the bulk of his range, you're torn between three-betting and smooth-calling.
Let's look at both carefully.

Three-Betting

If you three-bet, he will fold out the worst of his range and will continue with A-K, A-Q, K-Qs, AA-88, and some suited connectors.
Some of these will be four-bet, some of them will not.
If he folds, which is one of the better scenarios, you win a small 4xBB pot.
If he calls, you'll be playing out of position with a growing pot against a range that largely dominates you.
You beat his button-raising range, but his three-bet calling range is better than your hand.
Most of the time the flop is not going to help you; you'll be playing out of position against a decent TAG on a flop that didn't improve your hand against a range that largely dominates you.
The one positive aspect to three-betting is that you will win a number of pots before the flop - and when you do see the flop, you'll have the initiative.
However, the initiative is seldom enough to overcome playing out of position against another good player whose range beats you.
Thus, when you three-bet your goal is to get your opponent to fold.

Calling

Now let's look at the flat-call.
There are several plus sides to smooth-calling.
The main drawback of course is that you let your opponent take the lead in the hand.
On the plus side, you keep the pot small with a potentially dominated hand. Also your opponent will continue with the bulk of his range.
If his button-raising range is something like AA-22, A-Ks, 4-5s, A-Ko-6-7o, Axs, A-To-A-6o, K-Jo-T-8o, Q-9s-9-7s (most TAG's button ranges are similar), you're actually ahead of his range.
By smooth-calling you allow him to continue with his entire range, as opposed to three-betting infrared contact lenses, which lets him define his range to one that beats you.
Another positive of calling is if the flop comes ace-high, he'll continue his aggression with many worse aces than yours.
If you three-bet, he calls and the board comes ace-high, you'll often find yourself out-kicked at showdown.
By flat-calling you get your opponent to continue with worse hands than he would if you were to three-bet him, and you get to keep the pot small for when you're behind.
What you give up is your initiative in the hand. And in the end, the EV of calling versus three-betting is fairly close.
What you give up in post-flop EV by three-betting is made up all the times you win the hand before the flop.
What you give up in EV by not three-betting pre-flop is made up each time you flop a better hand than him and see a showdown.
Each side has its positives and negatives, with neither one showing a great advantage over the other.
The idea is simply to fully contemplate each decision and know what you are going to accomplish before you act.

Example 2

Game: $1/$2 No-Limit six-max; effective stacks: $200.
You have K♠ Q♠ on the button. It's folded to you and you make it $8.
The small blind folds and the big blind calls.
The big blind is your average fishy player. He calls too much pre-flop and calls too many streets with dominated hands.
In PokerTracker terms, he plays around 32/8/1.
The board comes 3♠ 4♠ T♣.
Your opponent checks and you ... ?
Well, this is an easy bet.
After taking the lead pre-flop and flopping the second-nut-flush draw and two overcards, you have a strong hand. This bet is a continuation bet/strong semi-bluff.
Your bet has a split goal - either way is good. If you bet and he folds, you win.
If you bet and he calls, you have a strong hand and are building a pot should you hit. So you bet $14 and he calls.
The turn brings the 9♥. Your opponent once again checks. You ... ?
Now you have the option of checking or betting card cheating.
You did pick up three more outs with the 9♥. Now any jack also gives you a straight.

Checking

By checking, you gain a free shot at your 12 outs to a near nut hand as well as six more outs to top pair.
However, if you check and the river blanks, you have a very small chance of winning the pot.
So what checking accomplishes is a free shot at your many outs.

Betting

Now the betting argument. Against a ten you have 18 outs.
Your equity in this hand is very strong.
Your opponent could also be calling with a wide range of hands on the flop.
He could have a mid pocket pair as well as a ten or maybe even overcards. He probably does not have an overpair.
This means you have 18 clear outs. You can also win this pot with a bet on the turn.
If your opponent was calling the flop really light, he'll likely fold to the turn bet.
Your goal in betting the turn is the exact same as when you bet the flop.
You don't mind if he calls because of your outs and you really don't mind if he folds.
You bet $35 and once again your opponent calls.
The river drops down the Q♣. There's $115 in the pot. Your opponent again checks.

Should you bet or check through?

Well, to make a properly informed decision you must look at what your opponent's range consists of.
You know your opponent is fairly bad. His flop call could mean anything. His turn call defines his range a little better.
He most likely has some kind of ten (AT-JT), JJ, a flush draw or Q-J for a straight draw.
Now you know what a check would accomplish. It will let you show down your hand and see if it is best.
Now, if you bet, you have to decide whether you're betting to make a better hand fold (not likely) or to make a worse hand call.
Obviously your bet will not make any better hand fold. So you have to decide if a worse hand will call.
Since you've determined your opponent is a bit of a calling station, you surmise he'll call with a worse hand.
Your goal, therefore, is to bet for value.
You bet $50 and your opponent calls with Q♥ J♦.
Success.

Conclusion

As you can see there's a lot beneath the surface of your average poker hand.
You must always be evaluating and reevaluating what your goals are in your hand.
It may start out as a bluff and by the end turn into a value bet.
So do yourself a favor. Stop just acting instinctually, and start giving each decision the attention it deserves.
Ask yourself why, and ask yourself what you hope to accomplish before you act.
It will help your game immensely.