As an engineer who's just starting out, I get no solicitations at all. I've heard about people being constantly contacted about work, but that's just not happening to me. If I lost my job, I'd have no idea what to do. How do you get on these people's radar? I'd love to feel more in control of my career instead of like my whole life depends on the good graces of my current boss.
1) They have a LinkedIn or Stack Overflow account.
2) They have dealt with a recruiter before, either looking for work or from cold calls.
I've had the (mis)fortune of both. The only people that ever look at my LinkedIn profile are recruiters, so I regularly get emails about crappy jobs. Hell, it's not unusual for a recruiter to offer me the same-level job at the company I already work at, sometimes even by phone...
It'll happen, so I won't worry too much about it. It's largely a talent market out there, and if you've spent enough time at a company that gets hounded by recruiters or a recruiter finds an online profile of yours you'll be on a "list" too.