This is perhaps the most important basic concept relating to strong post-flop play. It governs everything you do. What action to take as well as your bet sizing are both influenced by the hand you are attempting to represent.
Generally, when you are value betting you want your hand to look like a bluff so it is more likely to get called. And when you are bluffing you want your hand to appear like it is for value so you achieve more folds. I feel this basic concept is where a lot of players miss the boat and is what separates the very good players from the ones that are just clicking buttons.
The two areas of your game you need to be most aware of what you are representing is how you size your bets and what lines you take with particular hands. When considering a bluff, if you cannot credibly represent a strong hand with your perceived range on a particular board, then it is probably not a good idea to attempt a bluff. On the other hand, this is why you don't want to slow play when you do have a big hand in these spots either.
To maximize value with a very strong hand, then you want to try to get into the mind of your opponent and figure out what he would perceive a bluff line to look like. The key factor to remember is that most players think other players think like they do. In other words, when a player is attempting to decipher what you are doing they base their decisions on their own thought processes. Therefore, we should base our decisions on how an opponent thinks we will react based on how they would play in a similar situation. Most players deduces our thought process by using their own though process.
For example, if an opponent likes to bluff shove the river when a scare cards hits, then we should be less apt to bluff shove in a similar spot against him because he will tend to call there much lighter. This is because since he would bluff shove that spot, he believes everyone would do that there and will tend to be much more likely to look you up. Conversely, if a so-called scare card gives us a very strong hand, we should look to shove all-in rather than making a smaller value bet.
As you learn about the various player types, try to think about how each one of them would react in different scenarios both pre-flop and post-flop. Once you gain a feel for how these players think, then adjusting to them will become much easier.