The key here is generously: at least a half tablespoon of salt for every medium-sized eggplant. It seems excessive, but this salt will help to draw the bitter liquid out from the eggplant while simultaneously seasoning the eggplant from the inside out. It also helps the eggplant pieces stay more shapely and become tender during cooking instead of becoming water-logged and soggy.
Let the salted eggplant sit for at least 1/2 hour or up to 1 1/2 hours. You'll see beads of moisture start to form on the surface of the eggplant as it sits. Some of the pieces may start to look a little shriveled; this is fine.
When you're ready to cook, rinse the eggplant under cold water to remove the excess salt. Then press the eggplant between clean kitchen towels or paper towels to extract as much liquid as possible. This done, you're ready to cook.
Salting makes less of a difference when working with fresh, just-picked eggplants, but can really save the dish when working older vegetables. For me, this was the trick that got me over my fear of eggplants and taught me how to love these strange purple globes.
Have you ever tried salting your eggplant? Do you think it makes a difference?