Had many bad experiences with recruitment firms.

They insisted you to sign an agreement contract with silly terms such as need to pay for a placement fee, compensate them if you leave with X months, etc.

Most of them called them headhunter are actually telemarketer who just want a copy of your resume and has little or no knowledge on the industry they are helping to hire.

Some of them would tell you to lie about your working experiences so that you can secure the job in the interview.

My take now is:

1) "Hello, I am a headhunter", put down that phone instantly

2) Can you forward me a copy of your resume? Sure, give me a copy of the job description from the hiring company first

3) Accept invitation from linkedin from recruiters selectively

4) Let's talk. Sure, but never in your office, but at a time and place of my choice.