How is it determined who gets what and who pays for what in a divorce?

How is it determined who gets what and who pays for what in a divorce? He came into the marriage with nothing. Clothes, furniture, appliances, electronics, etc., nothing. I owned my own home for the 7 years we were together prior to marriage. The home was sold before the marriage. The house was in only my name, as was the equity check. We have since been married for 5 years. Our new homes down payment was used with my equity dollars. We are upside down in this house now due to the economy and Florida home values. The new home is in both our names. How do we split the 401K savings, stocks, etc. Does it matter what was saved and purchased during the marriage? Since we are over our heads in the home we are going to try to live together since we can't sell it, and we can't afford to take a loss either.