If no one has mentioned it yet, think about your shops appearance, does a person who is thinking about learning to dive want to walk in the door and stay for a half our or is does the place look, smell, and feel like a dump? – It should be:
Warm in the winter – In the North most shops I have seen save money on heat, does a customer want to try on a wet/dry suit when the shop is 50 degrees and you are in a sweatshirt?
Brightly lit – If I can’t see it, I can’t buy it
Have a changing room which is not the bathroom – A changing room is a changing room, No one wants to smell what you just did or see its smear in the bowl when trying on anything.
Have a bath room which has been cleaned this decade – Your wash room should not be used as the regulator cleaning area or look like the garages down the street.
Be dry – Keep the smell and wetness of your rental gear out of the show room
Have a good selection and be ready to order and work price vs. volume as best you can, You are competing with the internet, get used to it. What you have going for you is they have to come to you for air, but nothing else, even service can be done easily and sometimes cheaper using flat rate shipping to a shop across the country.
Do air fills quickly and at a reasonable price – These are your loss leaders, don’t loose money but it is not a profit center. Fills bring in the customers and allow time for them to look over all the small (and high markup) and big stuff – you do have a good selection of such, don’t you? This is where you have a captured customer for 10-15 minutes, use it.
Your service area should be clean, neat, and visible to the customer ( a window works well) – If it looks like my 7 year old runs it, why should I trust your work on my gear?
Make sure that the compressor is quiet so you don’t have the shout and the customer wants to stay and hear your pitch.
A coffee table on Saturday morning can go a long way to keeping people in your store.
Learn how to pitch your goods and services without it being a hard pitch. Do you like going into a car dealer or furniture store and have a sales person chasing you like a vulture after a sick animal?
Many dive shops are run by people with no training in retail and it shows. The above list is only a beginning, take a basic retail course at a college or university.