They sprout fine green leaves - similar to large chives in appearance. As the season progresses, the plant will develop a rosette of small shallot bulbs, held together at the bases. Mine usually number between 3 and 7 in a bunch. The bulbs tend to develop on or close to the soil surface - by the time the greens have died off completely, there is an easy to lift bunch of shallots just sitting there waiting.
After letting the harvested bulbs sit in a tray for a few days, I clean them up by removing a layer or so of the outer "skins" and trimming the roots, separating the bulbs at the same time. I then lay them out on a fresh tray, and leave them to finish drying somewhere cool and airy. I put the tray up on some blocks to ensure air flow underneath. They store pretty well - though best kept in cool, low humidity conditions. If only I had a root cellar!