Calling raises with low to mid pocket pairs

Hey all,
I have a question about calling raises with low to mid pairs! I have a real dilemma with this and was wondering what each of you do! If you answer,please answer in regards to early,middle,and late positions! O.K. How big of a raise would you call to try and hit trips on the flop, river and turn? I know if you hit there is potential for a huge payoff! But fishing for them could be costly as well! An example: I had pocket 7's in late position and had an early positioner raise 4 times the big blind with a caller in mid position! I know I was priced in to call, but had called several hands already tonight with pocket pairs to no avail! I guess I was gun shy to do it again!
i know there are further problems with chasing on the river and turn! I hardly ever hit trips after I miss on the flop. Now, if they both check on the flop I would certainly see a free card or make a continuation bet to take the pot. But,here again, that is risky when the cards on the flop will most likely be higher than my pocket pair!
I know I'm rambling but there are a lot of factors and it is difficult to decide what to do and I know every situation is different. I would just like some of your thoughts to help me through this!!
Player

first,if you meant pocket pairs,than it's not hiting trips but sets.trip means there are two cards which number eaual to one of your hole card.
I like pocket pairs.So long as my stack size is enough.I will call peflop raise even to 3BB.And of course,that is based on my stack size.That many times I can raises.If I am shock stack.I will call with higher ranks of pocket pairs.For example:above 77,or above 1010.

With a low pair, I will almost never call a raise, unless I know for sure that a guy is super-aggressive and puts in a raise every time then I might.

With middle pair, I will probably call a late position raise if there were a couple limpers in the pot with me, but not all the time.

The one thing that it seems like you aren't understanding is that just because you have a pocket pair doesn't mean that you are going to get a set. You have a 7.5:1 odds of hitting a set on the flop. After that, unless my pair filled some kind of a strong straight draw or I had middle pair that is still higher than any of the flop cards, I would not call any other raise past this point thinking I was going to hit that set.

Okay, I will call with most pocket pairs in late position, middle about 75% of the time in middle position, and with middle only about 20% of the time in early position. With these hands especially the lower pocket pairs, you almost need to hit set to have the best hand. Also if you don't flop it, fold it. Chasing down sets is something that should not be done, since you only have 2 outs to make your set.