It also depends on how many allowances your spouse takes. My husband takes the "recommended" number of allowances, so I have to withhold a ton extra since my income is all taxed under our maximum bracket. (I realize that's just a point of view, but it helps me adjust properly)

What I do is I use the IRS withholding calculator and figure out what are taxes are estimated to be. Then I write 99 on my w-4 and add 1/26 of the total estimated tax as additional amount to be taken out of my paycheck.

You don't have to take those allowances, it all depends on your tax situation. You should run the numbers a few ways and see what is best.

For the personal allowances worksheet what number should I write down? I am married to a spouse who earns more than me, and we have two children. I think I should put down 4 correct?

It seems like if you are single with no kids, it would be 1, married with a working spouse 2, then add how many kids you have? Is that correct?