The best weapon you can use in making a post-flop move is to have position. Here are some moves you can use post-flop to try and pick up chips without legitimate hands.
This flop looks like it hit the blinds in an unraised pot move: How many times have you completed the small blind or seen the flop out of the big blind and the flop came 8-5-3 and you check folded to the bet made from the button limper?
Most of the time it's very likely this flop missed the button, but they are taking advantage of their position. This move takes this into account and adds in the fact that a rag flop is more likely to hit a random blind hand than it is someone who has chosen voluntarily to put chips into the pot.
You can lead out and try and take the pot down right there. This is the more cost effective method of doing it because if your opponent raises you, you can release easily without a significant loss. However, the problem with this move is that your opponent might take advantage of your positional disadvantage and float you to see what you do on the turn. You can take this away from them by check raising. Check raising will cost more in chips if your opponent has a legitimate hand but it will also make it much harder for your opponent to proceed because you are representing true strength.
The float move: This is another popular move that is being used a lot, so be careful in using it. The way this move works is that you call a bet on the flop, in position, in order to try and take the pot away from them on the turn. When your opponent checks to you on the turn, they are most often telling you they no longer like their hand and are giving you an opportunity to take the pot from them.
The representing a hand move: This one's a bit harder to pull off and can be expensive because it requires you calling a bet in hopes that a certain card arrives. For example, let's say the flop comes with a straight and flush draw and you feel your opponent has something along the lines of top pair. You don't think you can use the float move successfully, but if the right card comes you can represent a hand that could induce a fold. If that straight card or flush card comes and your opponent checks or bets, you bet or make a raise telling them that you hit your hand. Often times you can get an opponent to lay down a legitimate hand in this situation. Of course, don't make the mistake of making this move against an opponent who has shown they can't fold if they have a piece of the flop.
The Main Holdem Strategy Index: The Great Game of Holdem