Severance offer, what should I ask for? - any advice?

My manager said the package is final, but the letter gives me time to review. I have been trying to stay organised about it. I do not want to leave money on the table. Did anyone negotiate and succeed?

An hour with an employment lawyer cost me a small fee and made me feel much safer about signing.

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