African Cichlids are the hot commodity for alot of newer fishkeepers these days. I'd suggest a African section, not just a tank of "Asst'd Africans

"
I too will suggest stocking species that the other LFS's in your area don't normally carry and hard to find species. Make a name for the shop locally and regionally as a shop with quality, healthy hard to find species.
Don't sell dyed or hybridized fish.
Meticulously maintain tanks and have a specific qaurantine section.
Have a "Foster Fish" area or tanks available, many people want to get rid of large fish or buy large fish. Sell these fish for the cost of your upkeep.
Be willing to special order customer request, customer should be required to place a conditionally-refundable* deposit on special orders.
*Refundable only if the fish don't arrive healthy and as ordered, I would go so far as to have a legal 'contract to buy' or pre-pay on expensive species or large orders.
I love the idea of a board listing "Janitorial crews", for various tank sizes, with a big educational caption on the bottom saying something like,
"There is no fish that eats POOP! Cleaning POOP is your job...
Check out our selection of Pythons and Gravel Vacs and other asst'd maintenance supplies."
I would like to see a board listing the steps necessary to keep healthy fish, something like,
(1) Have a idea of what fish you want, and purchase appropriate equipment.
(2) Fully cycle the tank, understand the Nitrogen cycle and importance of test kits.
(3) Buy your stock and acclimate properly.
(4)Have a regular weekly tank maintenance schedule.
ect ect......
My store and employees would provide sound advise and education.