sicilian defense

Can someone explain to me how you should play the sicilian defense after the initial move. I have problems with it even though it is supposed to be a great defense. 

aggressive and dynamic

it seems you are just starting out. Id work on tactics and look over symetrical 1.e4 games from the romantic era if I were you. worry about sicilian later.

Those are some very helpful replies.

The specific strategic goals depend on what variation you're playing, so some knowledge of that would help.  Generally speaking, most often you'll be playing an Open variation, in which White follows up with Nf3 & d4, you exchange your c-pawn for his d-pawn, and then expand on the queenside while building up pressure on the open c-file.  White counterattacks on the kingside, so it makes for an unbalanced game.

I dont think the sicilian is a good choice for sub 1800 level players.  Its far too complex/difficult and theory intense.

Hey Reb, how do you feel about a recommendation of the KIA for lower rateds, even beginners?

I think it's a bad idea but still I see it recommended in these forums often.

 I think its better to learn to play open positions when one is starting out.  The KIA is often very closed/positional and I think such positions are more difficult for beginning players to understand/play well. The appeal of the KIA and other openings like the Colle is that they can be played against pretty much any black response so lots of players are drawn to them as it seems to be less work involved.

As to the original question it is too broad.  How should you play after 1. e4 c5 ?

It depends on which system white plays and which one black plays.  The only answer that is correct but completely useless is You should play accurately.  The more helpful answer is to remember the sicilian relys on imbalances and counterattack.  You can't "Take it like a man" and then come back to wipe out an exhausted white.  You have to punch back from the beginning.