Layoff notice, what does the 60 days mean? - what worked for you?

My employer announced that the site will close and gave us written notice. I do not usually post, so bear with me. I do not know if I should start looking now or wait for severance news. Has anyone been through this?

Thanks for writing this out. I went through something close to it 2 months ago, and it settled down once I kept a simple log of every call and form.