You End up with a Middle Pair
Hitting on the middle pair is like being in halfway house. You have hit on the flop, so luck is looking at you kindly but on the other hand you also realize that you have a fair chance of being beaten.
If someone bets big before you, you should realize that they might possess a top pair, do not panic, act accordingly and throw the hand away. If no one has acted before you, stick to a modest bet to be on the safer side. This will give you the required information about the quality of your hand without throwing away a lot of chips, and might also take the pot then and there.
Anybody with a high pair or better would most likely raise the bet also serving as a pointer to you that you are already beaten. If on the other hand somebody calls, it might point to a flush or straight draw be sure that it is not slow-play or top pair with a poor kicker.
You End up with a Bottom Pair
This could be more complicated than you think, seeing as though you have hit on the flop it is not all that. It is a given that in normal play the best thing that can happen to you here is to watch out the turn for free and wait for trips or two pair to change this into a hand that is safely worth investing in. A bet, more so a bluff, with this hand is much better than a call as the bluff will at the least create the false impression of strength.
To put it more simply, playing these will push you further into riskier and unknown grounds. Most of the top players insist that they play bottom pairs on intuition, banking on their gut feeling to guide them to play it in certain conditions. If you are not all that indulgent to risk your money on a hunch, or are worried that you could be outplayed, fold and save your money for a more promising situation.
You End up with a Draw
Flopping an open-ended straight or 4 parts of a flush draw will quite rightly leave you in a shiver!
In case you flop a big draw, there are, to be brief, two lines of thought on how to play it. Both are equally valid. Based on the general cross-section of the company playing on the table and the method that best suits your kind of play, choose any of the two.
If you are hoping to get a free card to make your hand then the first thing on your agenda now should be to check the draw. Once you do this and also get lucky enough to hit, then be confident that you are back in the game and raise the stakes accordingly. This would be a good option for those who are passive players or are more careful with their chips.