Here are some of the reasons you should seldom slow-play.
1. You aren't getting more money into the pot. You need to build the pot early so your opponents will be more likely to call a real big bet later.
2. If you always make the continuation bet with marginal hands and slow-play the big ones, your marginal hands aren't disguised. Your opponents can better evaluate your hand.
3. Often on the Turn or River a scare card can hit and kill any action. If you made a great hand on the flop, the flop is probably coordinated. Any three coordinated cards have at least eight cards that fit and will kill subsequent action. The scarier the board the more action killer outs that are available. One of the killer outs will hit on the Turn about 15% of the time and 30% on the Turn and the River.
4. If the board is coordinated, your opponents are more likely to have a draw and will call your bets early but fold when they miss the draw. Bet it out.
5. A small Full House is even in jeopardy, and there is no nut Flush, or straight when the board pairs.
6. Even slow-playing, hoping for a check raise often reduces your EV. Unless you have a very aggressive opponent to your left, it is best to bet it out, and if he is that aggressive, bet it out and let him raise. Many astute players will fold to a check raise but call a reraise. (Check Raising is a powerful weapon, and like Nukes it should only be used to alert your opponents that it can be used.)
Of course there are times when slow-playing is the best play.
1. When you have a very aggressive player to your left and you know he will bet.
2. The game is very tight and none of your opponents can be expected to call a bet. (Actually, I suggest you change games in this situation.)
3. The board is very uncoordinated and your hand is well disguised. (In early position if the flop has produced a straight or flush draw, bet your sets. If the board is ragged, consider slow-playing your set. In late position, you first inclination should be to bet. Let them think you are trying to steal.)
4. Use the Check Raise when you know you will get raised and, your reraise will be called, or you can trap opponents that act after the original raiser. (If you have opponents between you and the probable raiser, bet it out and hope for the raise to set the trap. If the other opponents act after the probable raiser, go for the Check Raise.)
5. In limit poker, slow-playing on the flop is usually correct if your opponents can be expected to call a bet on the Turn when the bet size doubles.
To sum it up, slow-playing a big hand is often a bad proposition. You often leave money on the table. Your opponents may identify the pattern, and your continuation bets with weaker hands become vulnerable. I'm not suggesting that you never slow-play but your first inclination should always be to, BET IT OUT.