The form tells you that if you are exempt you would fill it out as per the instructions for that purpose. See the current Publication 505
If someone is claiming you or can claim you as a dependent on their tax return, you can't claim exemption from withholding if your income is more than $950.00 and includes more than $300.00 in unearned income such as dividends or interest.
On the form, there is a Personal Allowances Worksheet for you to fill out if you are not exempt.
There is a consideration for certain tax credits, itemized deductions, adjustment to income or a two earner (multiple jobs) situation.
Although you must complete all of the worksheets that apply, you can still claim zero or fewer allowances.
There are instructions for Head of Households and how to file for that, as well as provisions for children as dependents.
The form W4 instructions suggests that if you have a large amount of unearned income you might consider making estimated tax payments by taking advantage of the form 1040-es.
If you have more than one job or two spouses are earning it is suggested that it is better to take deductions for children from the pay check with the higher income.
To download a printable IRS Form W-4 Click on the image of the W4 form on the left.
Be sure to carefully read the instructions as they are on the form. If you feel that you want to file a volunteer withholding request, file the Form W4V .
Non resident aliens take notice
There is a special method for you to use in filling out the W-4 form, and you can read about it here on the IRS website.