Before creating a new account, it is best to avoid confusion with existing accounts.
Remember that for one inbox, you don't need a new account—you can use username+anything@gmail.com to create filters. To make sure you get the best setup, are you: Creating a personal account or a business account ? Using a computer or a mobile device ? login-new-gmail-account
Once your new account is active, you can easily switch between your old and new Gmail without logging out every time. Before creating a new account, it is best