Once you're armed with all of the information regarding odds and outs you need to be able to use it to help decide which plays are profitable and whether or not you should be betting in certain situations.
There are times when pot odds can be used to show that you HAVE to call, regardless of the strength of your hand. Suppose you were in a tournament and the blinds were 3,000 and 6,000. You are in the Big Blind and have posted the 6,000. A player in mid-position goes all in for 6,500 and another player calls that by posting 6,500. The small blind now also calls the extra 3,500 and the action is now on you.
Including your original big blind of 6,000 there is now 25,500 in the pot and all it is going to cost you to see the flop is another 500. You are therefore getting odds of over 50-1 on your extra 500 and MUST call without hesitation, regardless of what cards you're holding. It doesn't even matter if you've got 2-7 off-suit because there's no way you're going to be anything worse than a 10-1 underdog, yet you're getting 50-1 to call. That's pot odds of more than 5-1 in your favour! If you got lucky and flopped a full house you'd probably go on to win a pot of at least 26,000 and all for an extra bet of just 500.
That is an extreme example of what can happen but the principle always holds true. If you're always getting positive pot odds when you play, provided that you're playing with decent hands, then eventually you're going to be making money.
To give another example; Suppose you'd just seen the turn card and there was now 12,000 chips in the pot, with you still needing a card to make your flush. You can now work out where you stand and whether you should continue to draw for your flush.
Your opponent decides to go all in for their last 2,000 chips. That means there is 14,000 in the pot and you have to put in another 2,000 to see the river. That's 7-1 for your money. If you are drawing to a flush then you have nine outs and we can see by the outs and odds table this means you have a 19.6% chance of getting your card. That's approximately a 4-1 shot and considering that you are getting odds of 7-1 on your money you can see that you really have to make that call.
On the flip side of the coin, if somebody puts you all-in and you're only getting, say, 2-1 on your money then you should not be gambling if you know you've only got a 10% chance of winning the hand. 2-1 for your money on a 9-1 chance is NOT a good way to play poker, or any gambling game for that matter!
Also, if you're absolutely convinced that your opponent already has a powerful hand that you probably can't beat then no favourable pot odds should entice you to call. Good poker players will work out the right sort of raise to try and tempt you to call, because the pot odds are right, and that's where your poker instinct should tell you that you're being strung along or slow-played.
In the long run though, making the appropriate calls based on outs, odds and pot odds will work in your favour, as will folding your cards when you have a marginal hand and no good odds to call.
There are times in tournament play when you don't want to risk your chips, such as when you're protecting a small stack and don't wish to gamble, regardless of the favourable odds (perhaps when you're close to the pay-out structure?), but at all other times you should pay heed to them and act accordingly.