You are supposed to get a rebate form from either the manufacturers website or from the place you buy the product. Fill it out, carefully follow their instructions to the letter (or they will disqualify you), and mail it in. Then you get to wait for a check to come back. Sometimes it only takes a month. Sometimes it takes 3 months. Sometimes, they never come.
Personally, I act like there is no rebate. I do not factor it into the price decision, because I assume I will not get it. Then I fill out the paperwork, and occasionally, I get surprised.