I have a few ideas for your department that has worked in ours. The first is to start a firecorps junior firefighter or Explorer program to help recruit high school students. The second is to talk with your city or township officials to get see if you can get a copy of the list of people moving to your area and/or have reached voting age. This is a great resource that you can send use to mail out flyers to new people in your area. Keep in mind that your best recruits are already volunteering somewhere in your area and just need guidance to your department. Consider CPR/ First aid classes as an excellent way to find volunteers.