Drawing hands
You have to make an important distinction between the hands you do chose to play. Either they are hands that can win outright, or they are drawing hands. When you play an outright win hand you are trying to win with 1 pair, 2 pairs, trips or a set*. Outright winning hands are of course the big cards and the big pairs, AA, KK, AK and so on. Whenever you are playing hands like J10s, 78s and such, what you are really looking for is the 5 card winner, a flush or a straight, but in order to get value into drawing for this there have to be a certain amount of money in the pot.
Often forced to pay a bet or two
When drawing you are often forced to pay a bet or 2 on flop and a bet on the turn in order to make your hand and the more players who are paying to stay in, the more profitable your hand gets if it makes it. Occasionally you might win the hand if a J flops and no overcards come when you got J10s, but this is risky business and not the main reason why you chose to play this hand in the first place.
There are hands that are both outright win hands and strong drawing hand at the same time. AK suited has the best of both worlds. When you got this hand you are in great shape when you hit an A or K on the flop (top pair, top kicker), but if you don’t hit the flop you might be in a position to draw for straight or flush which both will be the nuts if you make it.
This is the reason why a number of players actually prefer to have AKs than AA in a multiway pot, of course if you do happen to have AKs while another player got AA, well that’s just not really preferable after all. Bottom line here is that AKs plays well no matter how many opponents you got with you in the hand. A top flop for AKs is (apart from the obvious AAx and KKx flop) when you flop top pair and 4 flush.
Another top drawing hand is J10s, but this has very little value as an outright winner. You can be almost 95 percent sure that when this hand makes a straight it will be the winner, and though you will not be drawing for the nutflush with a J high there is a great chance that you will win when the flush comes. One of the best flops here will be 10-x-x with 4 flush. Now you can hope to catch the flush, but any J or 10 later on will most likely win it for you also.
What your expecting
Every time you play a drawing hand you are hoping to either flop trips, or a made straight or flushdraw, whenever you do not you can safely throw your hand away. A made straight draw might be A-7-8 to your 9-10 while a flushdraw of course will be 2 of the same suit you are holding. Occasionally you flop a straight or a flush, and I cannot state the importance of betting HARD on a flop like this enough.
Whenever you have made a monster like this you can rest assure that other players now got draws against you, and yes, they have to pay to outdraw you here. When you got 8-9s and flop a flush and another card of the suit hits the board, you are almost certainly beat. It takes experience and a good feel not to throw your hand away. If this happens on the river, you have to grind your teeth and call a bet for pure value.
* Some players do not distinct a set and trips since they are both 3 of a kind. This is wrong. I consider trips to be when a player hold for instance AJ and the flop comes JJQ, a strong hand, but anyone with a J who hits his kicker beats the AJ as well as a player holding QQ. When you got a pocket pair and hits 3 of a kind on the flop, this is a set. Probably one of the strongest holdings in poker for so many reasons, not least for its deceptive value. Anyone can figure out that with 99K on the board and several raises, there is a good chance that someone got a 9, but it is not obvious that someone got 99 in a flop with A 9 5. A set got strong deceptive powers, it is very hard to beat and it can make a strong full house.