[codingdave]

I politely tell them where I am at in my career, what I would need from a position to make it worth discussing, and ask them whether they believe the opportunity they had in mind makes it worth talking to each other.

I don't share details about my salary - I just say I'm paid above market and would still need a raise. This weeds out most run-of-the-mill recruiters just looking to fill your average coder job. The ones who really have a good opportunity will tell me so and we'll talk. The one who don't usually still appreciate being told where I am at, so they know when I would want to talk.

I usually also tell them that if the current opportunity isn't a match, call me again in 6 months anyway, just in case my current project doesn't go well. This gives me a nice safety net if my job changes, and over time builds up a decent network of recruiters that I can just write back to if I ever were to want a change.