I’ve been a group ex instructor (in mumbai, India) since the last 16 years teaching a cross training class (aerobics, step, tabata, bootcamp, etc). While my classes bring in an average number of people, i would like to reach out to more since i have so much to offer in terms of knowledge and experience.
The best marketing you can do is probably grass-roots marketing where by you reach out to the local community by placing business cards in the area and with selected partners like hairdressers, beauty salons etc. Try to stike a deal with these establishments like a special offer for their customers or 20% off. I also used to run a free fitness class in my local church hall. I didn’t charge but the amount of work I got from clients off the back of this was really good.
In addition to the suggestions Lori and Ariadne mentioned, you could try to advertise to the communities and neighborhoods where personnel from the different embassies and consulates reside. Another option would be to partnered up with some of the resorts that might be close to you and offer classes at their locations. Mumbai can be a very popular destination for people from around the world and these resorts are always looking for experienced instructors like yourself.