[Doc]

I think you've got to understand what sort of flop you want and how often you'll get it.

Basically hands will improve in 3 ways:

1) Making pairs (or higher)
2) Making straights
3) Making flushes

Taking each in turn:
1) The higher your cards the better your pair (and kicker) will be. If you start with a pair, then you have a much better chance of making trips (which will also be well hidden), so that is even stronger.
2) The closer the cards are the more straights they'll make, and the more of those that will be nut straights. If your lowest card is higher than a 9, then every straight they make is the nut straight
3) the higher the cards the more likely they are to make the nut flush

Connected cards, suited cards and pairs (unless they also have good high card strength) will usually not make the strongest hand on the flop, or even make a good draw. Since they will therefore have to be folded quite often, you need to get a good price to enter the pot. The more players already in, the stronger the guarantee that you get this, but if the table conditions are right, then you can play with fewer people currently in the pot.

e.g. at a loose passive table, I'd be quite happy to play KTs from early position, but I know I'm going to need a really good hand/draw to continue