How to become a case manager

I want to know how to become a case manager. I have looked on the internet and saw that there are schools where you can get certification or you can get an advanced degree. Which is better from a highering standpoint? Also, the how long do you have to work as a nurse to be a case manager?
thanks is advance!
I don't know if there are specific "rules" about how many years' experience you must have before applying for case manager. But think about it...the employer is certain to want a decent amount of past experience in order for the CM to be able to use judgment in deciding necessary vs. unnecessary treatments, how to best guide a patient's course of care, etc.Be careful. In my opinion, case managers have to walk a very fine line between protecting the patient's interests (being the advocate) and adhering to the employer's bottom line.

I have been a case manager for the past 2 years. I have an associates degree and when I got the job I had been a nurse for 3 years (MD office a few months, developmentally disabled clients in group homes for lil over 2 yrs). I was a case manger for a home based services program. There are case manager jobs for Hospice, home health, hospitals, etc. The hospitals seem to want BSN degree or a lot of experience. Anytime I put in "RN" on job sites, case manager jobs show up too. I have really enjoyed it...though I am laid off now since the program I worked for ended. I have an interview next week though.