I know it's hard to define value of a pre-flop hand, but I'm struggling at the moment to know how to play KQ, KJ and QJ, especially the former (the latter two I will lay down out of position or facing a raise, unless they are suited and I have good reason for wanting to see a flop).

KQ is dominated by AK and AQ, so does this mean it's as strong as AJ? or is it weaker as it doesn't have the high card potential, or is it stronger because the straight potential is higher? In what circumstances would people fold KQ? What difference does it being suited make?

Contriubtions gratefully received!