Nothing other than high-speed traffic kills Walk Appeal more than gaps in street frontages, otherwise known as "snaggletooth streetscapes." The easiest way to begin to heal downtown streets is with food carts and shop sheds. The best sites are those where large chunks of buildings have been demolished in the middle of a block but the end buildings are still intact because corner buildings have more street presence because they're visible on both sides of the intersection. Most downtown streets have wider sidewalks than residential streets, and should have regular street trees. Locate the food carts and shop sheds just inside the building lots so you have the full public frontage for places to order food, then sit in the shade of the street trees to eat it. And string lights along the cart & shed fronts extends sales into the evening, ideally strung through the tree limbs like these at Seaside.
You don't have to start big with food carts. Seaside started with just one. People loved it so they brought in more, creating today's interesting & delicious street frontage. Even as great as Central Square is, the Walk Appeal of 30-A clearly benefits from the strong frontage of carts and sheds. And remember that food carts are highly mobile, and usually still have their wheels attached. Shop sheds are almost as mobile, so start with blocks which need new frontages the most, then when they're redeveloped into more substantial structures the pioneering carts and sheds can be moved to the next most important blocks. Wash, rinse, and repeat.
Seaside's Perspicacity had classic shop sheds, built of just a few studs, some plywood, and metal roofing. They were as close to free as stores can be, but with world-class charm. Unlike food carts, which might have baths inside, you do need a nearby bath pavilion with shop sheds. But beware: Perspicacity was so charming that it took decades longer to redevelop it than Town Founders Robert and Daryl Davis planned because every time the subject came up, there were huge protests from the legions of people who loved it so much.
If you're around food carts, food courts, or food halls, notice who's there. Places people can go and choose what they want to eat, then convene with their friends around a picnic table is native territory of young talent, so healing frontages is a strong move all around. So food carts (and courts) and shop sheds don't just heal the street frontages for people who already live in town, but they also attract new residents who will help grow the town's economy.
Downtown Top Ten Series Posts
#7 - Complete Street Tree Network