Everyone talks about the "idiot" beginner so why not have a wall or part of one that has a list of all the freshwater fish you carry down the side and across the top with some kind of color scheme to tell them if the fish are compatible. Same thing can be done with inverts, salwater, crustaceans, etc.
Also, offer a product that is quality that will do the job, not just one with the name. Some people with want the name and will only buy a certain name but others, like me, want something that will do the job and not pay double for the name.
To get the business of the "established" aquarium nut, offer custom made tanks and hoods. If I was close enough I would definately love to have that job.
Have tanks in your show room that are just that, show tanks. My
lfs doesn't have anything like this and their fish are always changing. Set up as many as you think are needed to show community, agressive, freshwater, saltwater, inverts, crustaceans etc. This "shows" how it could be done so a person doesn't go in, get their stuff and try to put it together like a jungle gym without the instructions.
Last thing, Kits are cool, beginner or expert but don't make a kit just to make one. My local fish store offer a 10% discount on any tank bought if you get most of the materials from them. This allows them and us to make decisions based on the type of fish we want instead of a tank that just looks good and is a little cheaper than buying all the stuff seperately.
One more thing, make sure that your customers know they can bring back anything you sell and they can bring any aquarium related animal to you so it can be dealt with properly instead of winding up in the local pond.