regarding KJo--
early position at a 9-handed table: fold it almost always. easily dominated, lots of players still to act, and you can't stand a re-raise pretty much ever
middle position at a 9-handed table: depends on your exact position, table conditions, tightness of the blinds, etc. if someone raised before you, fold except in very rare cases (like they're a maniac who raises very very wide). when not facing a raise in front it hinges on the conditions i mentioned; sometimes it's a raise, sometimes it's a fold. the more experience you get, the better idea you'll have. it's not a good hand to open-limp with because if you get a raise behind, you really don't know if they're just attacking/isolating your limp or if they really have a good hand. once you limpcall and flop top pair, you have no idea where the hell you're at because they could easily have you outkicked or have an overpair. open-raising (especially with this type of hand) is important for defining your opponents ranges and avoiding trouble when you get 3bet
late position at a 9-handed table: pretty strong hand to open with; always worth an open-raise and usually an isolation raise if someone limped in. if a raise already came from EP or even MP it's a fold nearly every time
with fewer players you of course have to adjust your standards a little bit. in first position at a 6-handed table i'm still folding
usually, but any position after that it's probably worth an open-raise
KJ suited is not all that different. in some marginal spots where you might not play KJo, KJs might be worth a play, especially with deep stacks (like in cash games) where the added flush possibilities are worth quite a bit in implied
odds
usually they're good hands for being aggressive with in late position, and a good hand to get you in trouble in early position. hope this helped a little