You can have an unlimited number of judgments and garnihment orders, but only one can be paid at a time. the percentage they can take will depend on the type of debt. A "normal" judgment will generally take about 10% of gross pay, but it will be higher if the judgment is for child support arrears or student loan debt.
The amounts that can be taken from your wages to satisfy a garnishment depend on how much you make. Also, this number will change in July 2010, so I am going to give you the new numbers, which in many States will equal or be less then the current minimum wage in your State.
The law that controls garnishments is the federal “Consumer Credit Protection Act” 15 USC §§ 1671-1677. It protects a portion of the wages based on the following schedule that is tied to the federal minimum wage. On July 23, 2009 the minimum wage increases to $7.25 per hour. (You can use this number to estimate the current amount protected).
The amount of disposable income that cannot be garnished on or after that date is $217.50, or 30 hours at the Federal minimum wage for the week in question.
Only the amount over that can begin to be garnished. It is your employers’ duty to determine the appropriate amount of the garnishment, and not just rely on an order from a court.
Only the amount over $217.50 can be subject to the garnishment when total compensation is less than $290.00. If disposable earnings are more than $290.00 in any given week up to 25% of the wages can be garnished under federal standards. However State restrictions on garnishment should be checked in every case, as they may provide greater protection.
Conversely in many Sates Child Support payments or arrears are subject to higher maximum withholding standards.
Disclaimer: This answer does not constitute legal advice. I am admitted in the States of New York, New Jersey and Massachusetts only and make no attempt to opine on matters of law that are not relevant to those three States. This advice is based on general principles of law that may or may not relate to your specific situation. Facts and laws change and these possible changes will affect the advice provided here. Consult an attorney in your locale before you act on any of this advice. You should not rely on this advice alone and nothing in these communications creates an attorney client relationship. The opinions expressed herein are those of the author only and the fact that he has worked as an Assistant District Attorney; State Supreme Court Clerk; Special Assistant United States Attorney (Hawaii); Assistant Cornell University Counsel or Judge Advocate, United States Marine Corps should not be relied upon to assume that these statements reflect the policy of these organizations.