I am about to write my first employee paycheck and I don't know how much to withhold or how to find out. Washington state resident, one exemption. I'll probably end up using a payroll service or payroll software, but in the meantime, I have to pay her to morrow!

I am sorry you should not be hiring someone unless you already knew.

First you have to pay out of your money 7.5 percent into the social security, and deduct from their pay another 7.5 percent.
Then you will use a federral tax chart, ( gotten from the IRS) as to withholdings for federal. Next you use a tax charge you get from your state tax department for the state tax.

Is 7.5 percent for all states? I live in New Jersey and I am thinking about hireing a employee.