I’m Getting Married and Have No Idea What I Need to get the License — HELP!

I've heard of a lot of people that are getting married on 12/12/12. That actually happens to be our 4 year anniversary. So my fiance and I plan on going down to the Clerk and Recorders office to get our marriage license. But what do I need?

I'm  not sure if I need to have a witness on hand. Do we each need to have our own witness? I've heard that some states make you give a blood sample. Why would they need a blood sample? Do I have to give a blood sample in Colorado?

I have so many questions and not enough answers so I need your help. How much does it cost? Do I bring a priest with me? I obviously will need an I.D. of some sort. But do they need a Birth Certificate or a Social Security Card?

All you married and divorced folks that have been through this know the ropes. So help a buddy out so I don't mess this up LOL. I do know that Cousins can get married and that same sex can't. I also know there are some Common Law marriage laws that are pretty interesting. But none of that helps me. Give me your feedback below.