Here are the main ways of doing this that I've encountered. I've met advocates of each.

1. Keep your finances separate, with your own paychecks going into your own bank accounts, retirement funds and everything. When joint bills come up either pay half each or have one pay, and keep track to make sure they are split evenly overall.
2. Have one joint bank account. All income gets deposited there and all bills come out of it. Usually you would have to make some agreement as to how much money each person can spend without having to consult the other. Optionally each person may have an 'allowance' which they can spend with no questions asked.
3. Three bank accounts. Each person pays their own paycheck into their own account, and makes a contribution to the joint one. Joint expenses come from the joint account.

Here are the main ways of doing this that I've encountered. I've met advocates of each.

1. Keep your finances separate, with your own paychecks going into your own bank accounts, retirement funds and everything. When joint bills come up either pay half each or have one pay, and keep track to make sure they are split evenly overall.
2. Have one joint bank account. All income gets deposited there and all bills come out of it. Usually you would have to make some agreement as to how much money each person can spend without having to consult the other. Optionally each person may have an 'allowance' which they can spend with no questions asked.
3. Three bank accounts. Each person pays their own paycheck into their own account, and makes a contribution to the joint one. Joint expenses come from the joint account.

You might be interested in this set of articles: http://www.slate.com/id/2281885/ which looks at some different ways of doing this and the financial - and other - effects.