Are certifications worth it while job hunting? (update)

I saw that many postings ask for a specific certification. I am unsure whether employers value it. Which ones are overrated?

Check a dozen job postings first. If most ask for the same certificate, it is probably worth it.

Thanks for writing this out. I went through something close to it 14 months ago, and it got easier once I kept a simple log of every call and form.