Matt Laur , Jul 21, 2010; 07:46 p.m.
It would be rather unusual for an advertisement (for a perfume, for example) to display the name and web site of a photographer. The exception might be when the advertiser in question is deliberately leveraging the celebrity of the photographer as part of their campaign.
You need to read up on copyright and licensing/usage so that you have the vocabulary at your disposal when negotiating something like this.
When you shoot, you own the copyrights. That's pretty much the end of that, unless you are essentially on someone's payroll while you do it, or you expressly assign those rights to someone else (generally, just don't do that). When a business is going to use your images, you are granting them a license to do so. You need to put that license, and its limitations/obligations in writing. That license may give them exclusive use of the images, or it may do so with you remaining able to use them for portfolio/promotional use. How much you charge depends, in part, on how valuable it is to you to retain your own use of the images.