How do I go about getting a divorce?

I have been married for 4 years and have now had enough. I have come to see that my husband does not value myself or our vows and I would like to know how to get a quick divorce.  There are other factors to this issue as we have meddling inlaws who my huband gets defensive if they wrong me and I talk to him about it.  I have had enough and would like to just move on.  There are kids involved but I think that they can see that he nor his family treat me with the respect I deserve.  There is no physical abuse but I have recently come to discover that my husband took my son and got him tattooed against my wishes.  AND he only did it because our son wanted one.  It is small and on his left hand.  This is the last straw for me...my son is only 9 years old.  I cant deal with my husband anymore.  Can someone please tell me the steps I have to take to start the process of divorce and the costs too.