Many things impact how much you may need to have withheld including any credits you have be eligible for and whether or not you tax liability will be based on more than one income.
You might try using the W-4 Calculator tool. This will give you a better understanding of all of the things that go into calculating your proper withholding amount, and you can use it throughout the year to adjust your withholding if your circumstance changes.
Hope this helps!
