Several promoting books and reports on this issue state as following:

"SAVE UP TO 20 PERCENT ON ALL OF YOUR ADVERTISING PROGRAMS"

For sure, it iseffective, legitimate and also practical, but while this is a promise, it involves pros and cons which are obvious. Most magazines allow you the standard 15% commission and an extra 2% credit discount by setting up an advertising agency and by placing your ads under the name of your agency. For a yearly advertising budget of $5,000, this means a saving of $850 per year.

The downside of this operation is represented by the initial cost of establishing the new advertising agency, which, even if it’s not too difficult, it involves precious time. In order to initiate an ad agency you have to get a name for it which regularly is different than the one of the main business name. For instance, if your firm name is ABC and your name is Michael Denver, you may you’re your agency “Michael Denver Advertising” or The M.D. Advertising Agency. The physical address of the agency must be different than the company's address, but this issue can be done by renting a PO BOX for the advertising agency and using your home address for the other.

The next you have to do is to open a separate bank account under the agency name and that’s because all the advertising revenues will be issued thru your ad agency and you have to register your agency as another business.

And now, once these details have been established, feel ready to begin placing ads. You must have insertion order forms printed with the address and the name of your advertising agency. This will not be a problem if your advertising program implies only a few publications, but if you expand your business into more than 50 - 60 magazines, it can really become. But, sure, while the business get larger and larger, a hired secretary could take care of that stuff.
Good luck!