Don't forget to apply your implied odds. A turn call with a 5:1 draw can profitably made with only 3.5-4:1 pot odds.

Top pair outs are usually only worth about half an out each. 2 overs is worth between 3 and 4 outs, not nearly 6. You have 6 outs to top pair, but that will not hold up more than 2/3 or so of the time (very dependant on the board).

Two pair and trip outs are much closer to full value. If you have a pair on the flop, you should count your hand for 4+ outs (if you knew improving would win it would be 5).

Basically, the stronger the hand you are drawing to, the closer to full value your outs have. Obviously draws to the nuts with no outs giving a possibility of a second best hand have full value outs. If your draw is not to the nuts, your outs do not have full value. This is crucially important. Much more so for limit than no-limit, but still very important for no-limit. An example ... you flop an OESD but there are 2 to a flush on board. You have 8 outs to the straight, but 2 of these put 3 flush cards on board. Depending on the # of people in the pot, these 2 cards must be discounted by 1/4-3/4 of an out each. Your 8 out draw may really only be worth about 6.5 outs. A big enough difference to frequently weigh decisions from calls to folds or raises to calls.