In order to experience some Tax relief, you should adjust your withholding if there is going to be a significant change in the anticipated tax you will owe for the following year.
Tax credits such as child tax, Hope Scholarship and lifetime learning should also reduce your tax and offer some Tax relief.
By decreasing you withholding you might be able to benefit from lower taxes throughout the year, but an increase might also be wise if any previously claimed credits and deductions are no longer available to you.
It is also wise to increase your withholding if you expect and increase in non-wage income.
The form W-4 includes clear instructions on how to go about this.
In order to ensure that your tax withholdings provide maximum Tax relief, you should ensure that your withholdings help you meet the existing tax requirements and that at the end of the year you have met at least 90% of your current or previous tax year liability.
If you have only joined an employer part of the way through the year, you may also request that your employer base your withholding on the "part-year" method.
If you are getting married in during the tax year, and might be looking for some Tax relief, it might also be a good idea to change your withholding.
It depends entirely upon how much you will be earning as a married couple and is entirely up to you.
But if you have a substantial increase in earning it would more than likely be the best course of action to change your withholding.
You should ideally we within $1,000 of your tax liability for the year end.