How should I contact a previous employer for a job after being laid off from my current employer?

I was recently laid off from my current job. What is the best approach for contacting a previous employer to see if there are any open positions? What should I say? What is the best way to get in contact?|||call them as if you were a new employee. you dont get special treatment just because you worked there before. you have to go through the same steps as if you have never worked there. so i would go through HR if that is where you got the first application....