I have to disagree with this... to an extent. When you claim 0, you are essentially lending the government money at 0% interest. In fact, the real (nominal minus inflation) return you receive during income tax season will be less than the additional real value you withheld over the course of the year -- because of inflation.

Claiming 0 is for people who are not "savers" -- that is, people who aren't so well at saving or investing money in any interest-bearing account.

I recommend claiming the maximum allowances in which you are permitted to do so (probably 1, in most cases). In an ideal scenario, you would place the additional income you receive in each paycheck into an interest-bearing account; thus, when tax season rolls around you have enough money to pay off any tax dues. You'll actually have more -- the power of compounding interest comes into play. Of course, this is in an ideal world.

To summarize, my basic tenant is as follows: if you're a saver, claim maximum allowed. If not, claim 0.