I worked in accounting for many years and did a lot of payroll, so I had to deal with taking garnishment out of people's paycheck. Unless it's the IRS or other government agency the creditor you owe must have had sued you and won a judgement against you in court to be able to garnish your wages. Legally you cannot be garnished more than 25% of your net pay each pay period.

Basically the court system will send notification to your employer regarding the garnishment. (I.e., who the creditor is that you owe, how much you owe, how much money to take out of your paycheck and how many pay periods they are to garnish your wages until the debt is paid back) after that it's their job to take out the money and send it to your creditor each month.

Keep track of your pay stubs so you can monitor the garnishment yourself. It's always good to have a record of it yourself.