Your tax liability, put in the simplest of terms, is a function of your taxable income and how much money you put in (withholding, ECT).
Add up both your incomes, subtract the standard deduction for married filing jointly for 2010 $11,400 and the two exemptions you get $3,650 each. = $7,300
this will give you an approximate no deduction taxable income X- $11,400-$$7,300 = taxable income
Then find a 2010 tax table for married filing joint returns for your taxable income. to get the tax
Compare that to the total of your withholding if the withholding is more then the tax you get a refund. Less then you owe.
Unfortunately most newlyweds suffer from whats called the marriage penalty. But you were wise to carry zero dependents make sure to change it early in 2010 to married 0 dependents if you want the best chance of a refund.
Hope this helped