lol at the some of these responses.
There are very different circumstances. The only way it should come out of your wage, is if you're on a contract and even then, you shouldn't be on less, if you are why would you want to do it? My agency charges my employer x and I take y, they get the difference. I negotiate y to as much as I can.
Normally for recruiting though, it's a flat fee of 10-20% paid (normally in stages and sometimes have clauses that the recruited party has to have worked in their new position for 6months before the final invoice is paid, to stop companies losing out after they paid to recruit someone).
Headhunting is like the above, but more targeted to what the company is looking for, not the scatter approach that would be used above, sending as many CVs in as possible, they search for people in headhunting to find the right one and we used to charge 33% in 3 stages. Like the above, it is based on the package salary (sometimes base, depends) of the position you're recruiting for. e.g. 100k salary job, we would have got 11k start the search, 11k for a shortlist of candidates and 11k when they'd been placed for 6 months.
You should never have money taken off, as the recruited party, or headhunted party. If you have, or do, then I would run a mile.