Planing hands like KJo,K10o,Q10o...etc

I have been playing poker for about a year but have just recently started studying the game. In the past I would play hands like KJo and k10o fairly strong before the flop. If I were to hit either pair I would continue to play it strong. Time after time I would be shown a better kicker or get drawn out to a biger pair. Of course I would also run it to the situations where I end up with two pair or a straight. Because of this it seems to me that these play similar to a middle PP. If they hit big on the flop it can be a strong hand but with out a lot of help these hands will end up costing you. Is there a theory on how these hand should be played? It seems from early position they are pretty much trash. In middle to late position they are worth limping and potentially a raise every once in a while to change it up. This is one of may parts of my game that could use some suggestions.

Both of those hands are pretty weak. I'd limp with both and throw either away to a raise. I wouldn't raise with either unless it was KJs in a short handed game. Even if you hit you have to be willing to throw away your pair if you sense you are beat.

Depends on the table texture. QTo can be a monster when you have a 80% VP$IP fish to your right and mouses behind. Mostly I fold these from EP and limp or openraise with them from LP.

play them smart, think about what the hands are worth. In UTG let the hand go or maybe limp dont push them to hard, fold to all raises unless you can put them on a smaller pocket pair and you like to race. Otherwise while in position to an unopened pot raise.

They get stronger (as above) with fewer people at the table. Also if you're short stacked. Barring those situations, I don't think you lose much letting 'em go, especially EP.

In late with early folders and a mid caller or two, they're raisable. If the flop touches one of 'em you're pretty much required to bet big and drive off the Ax guys. If called on the flop, I think you bite the bullet and check it down if you can.

Not worthless hands but you have to know how and when to play them. Few hands in hold 'em are automatic bet-or-fold type hands. Just now as I was typing this, I was dealt K-10, gave it a small raise pre-flop, hit top pair (10s) with my king kicker on the flop, and bet everyone out right there. Perfectly acceptable play for king-ten. You can play king-jack the same way, just bear in mind you'd rather make top pair with the jack than the king. It also has better straight possibilities than king-10.