How much room is there after an offer? (update)

It is the first offer in 12 months and I do not want to mess it up. Any experience at all would help. The hiring manager was friendly and open. Did you negotiate?

Most employers expect a short conversation. Mine did not even blink.

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.