Here is more about negotiating in general (including the "never give a number first" thing): https://news.ycombinator.com/item?id=7713290

That's a great resource. Most of those are pretty simple to live by and he even warns about potential situations that may occur.

But what to say when they ask your current salary?

I would never share my current salary with anyone that can use it against me in negotiation.

If a recruiter asks, I tell them I'm not comfortable sharing it. If they press, I tell them that I only discuss numbers once the company and I both agree there is a mutual fit.

No one has ever told me they will not proceed without my current salary, but if it ever came to that I would thank them for their time and hang up.

Isn't there a lot of potential to waste time that way though? If they're expecting to pay 80K and you're expecting 140K?

Then they should say what they are offering. Don't forget: they could give a number, too.

This is a good policy. I know it's an unwritten rule that you don't tell someone your current salary when you're interviewing for a job but I like the way you put it. My professor last year said if there is a required field on a form you need to fill out then just put $1 for your salary. I've always appreciated that and followed it.