Noob pre-flop strategy question

SO I have just started my online play - so far so good - though only through 100 hands.

My question is this - as a general rule, in limit poker, if there are only folds/limpers in front of me, is it generally correct to enter the pot with a raise?

The way I see it, position and reads on the table largely determine what hands you will enter with - so assuming you have a hand that you want to enter the pot with, does it not generally follow that you should enter with a raise?

If so, what would be the exceptions to this rule? One that I can think of right off the bat is if you are on the button, or in the SB or BB and there have been several limpers in front of you and you do not have a premium holding - you may want to limp in cheap because of the size of the pot.

Otherwise, it seems to me that a raise is generally appropriate.