Seminar time and location are important. As for the venue, the more upscale, the better, and it should be easily accessible by car. Once again, we're talking about selling. If the perceived reward for the attendee is better than the difficulty it takes to get there, they will come. If the perceived value is not worth the difficulty it takes to attend, they won't come.
Many retirees attend several seminars before deciding on an advisor.
Expect to see some attendees more than once especially if you are feeding them. That, too, is part of the game. You can make the expense of serving a meal work for you. For example, I go from table to table, making sure to speak to every attendee. That personal touch has helped us develop many new clients.