What happens when you get a marijuana possession citation?

It depends upon where you are (Like if your black or Mexican, if your white you get a warning, if your anyother color you go to jail). All state laws are different and local policies may vary. In most areas, a citation usually results in a simple fine. In some areas, the person may be required to attend classes on drug abuse. Whether it stays on your permanent record also varies by where you are.

http://www.norml.org has a library where you can check the laws in your state.