At the top of the list should be any schools that offer a curriculum in financial planning. In our case we have had many interns from Wright State in Dayton, Purdue and the business school at Miami University of Ohio. Then send a letter to them expressing your interest in offering internship opportunities. This letter must be crafted to indicate that you are offering an educational opportunity, not a chance for them to do some filing for you. A secretary can call the schools and winnow through the voice mail to get the exact title and address of the persons you want to contact.
Some schools even have an intern placement office.
Put all of them on a mailing list, and start sending your newsletter, etc. You will not be overflowed with interns at first, but gradually they will come. However, you need to be ready to respond. Quite a number have subsequently become employees and we have enjoyed the association. You must continue to re-contact all the schools in order to have top of mind awareness on your internship opportunities.