Some thoughts:
Word of mouth is, by far, the best advertising
Figure out the most effective(and cost effective) advertising mechanism otherwise.
Being located at an attractive location is an advantage. Example, I want to dive Dominica and may be able to combine an advanced course with an extended freediving stay.
Tie your operation to other activities to provide options for nondiving significant others as well as make your courses more appealing to divers interested in things in addition to diving(believe it or not, they do exist)
Specialize in something that will bring you a higher skilled(and moneyed) clientele. Example, I'm looking for an instructor who knows a lot about diving half lung(aka FRZ) as a normal, all the time, diving style, not just for training. That is way too specialized, but you get the idea.
Become a presence on Websites that divers frequent, providing useful information. Example, Dano of Mako, is a frequent DB contributor. I suspect that brings him a lot of business, including some of mine.
upsers account