I just thought of this while doing our taxes. We were getting such a big refund several years ago and I wanted to have that money during the year, not give it to the government. I filled out a new W4 after our first, but claiming the number of dependants they told us was still not enough to avoid a big refund. I filled out another one with an extra exemption and that was better. After we had 3 dc we no longer had any federal tax witheld. We still get a refund, I guess it's of FICA/Medicare taxes. I don't think we can avoid having those witheld.
Just wanted to pass that along as some people might like to have as much money in their paychecks as possible.
Maybe this will help?
How to Fill Out Form W-4
I remember printing ours from TurboTax and dh taking it to work. There are online places to fill out and print one.