Assuming this job offer actually comes…should I really try to negotiate salary? And how??

I’ve been unemployed for closing in on 2 months but finally have a verbal offer on the table. Assuming they aren’t treacherous bastards and actually get back to me this week with the offer letter, I’m set to be offered $80k.

I’ve never tried to negotiate salary before but I’m wondering if I shouldn’t try it this time around. I would be taking a $5k pay cut from my previous job but the idea of trying to negotiate to get that back kinda terrifies me.

How do you know or even find out if there is room for negotiation in a given situation? And then how do you negotiate a higher salary without pissing off the prospective employer and having them retract the offer entirely?