Volunteer. Many MS, HS, community centers, church daycare/schools, etc. are now require by their insurance companies to get background checks for anyone working with their kids. Call these places, volunteer to get background checked, ask if you can volunteer in some capacity with fitness, and casually talk to the kids about your gym.
Partnerships. If you have other small businesses nearby, ask if they would be willing to handout a free or reduce trial class card to their customers if you handout something similar for them.
Social media. Be the local go to SM guy that gives tips and drills and have your business name in the background.
Interact and engage. If your schools or local community have fairs, ask if you can set up a booth. Engage with parents while waiting in lines and have a business card ready to hand them. Be available, and patient, for questions and teaching parents along with the kids about AS cheer.
Website and reviews. Make sure you have an informative website and encourage happy customers to provide good reviews. Be transparent about goals and money.
If you are located in a warehouse or a storefront that is not easily seen, consider information business flags or signs, near the main road.
Get creative. Renting out space for birthday parties, scouts to work on fitness badges, moms/dads to line dance, yoga, pilates, zumba, scrapbook...anything that can get your business known in the community is going to help you with word of mouth.