Greens of all kinds should be first chopped and then submerged in a large bowl of water and swished around vigorously, then scooped out, not strained. Change the water two or three times and repeat until no grit remains at the bottom of the bowl, then strain the greens in a colander and dry on a kitchen towel or in a salad spinner.
Most varieties of eggplant (except the Japanese type) should be salted before use. Sprinkle the eggplant slices with salt and leave them in a colander for 20 minutes until beads of moisture form, or else soak them in salted water then pat dry before proceeding. This is especially important for bitter or seedy varieties of eggplant. It also helps reduce the oil absorbed when frying.
When tomatoes are in season, liquefy them in a blender (crush slightly with your hands first) or grate them with a cheese grater, then strain for use in stews. If tomatoes are not in season, substitute tomato paste diluted in water or unseasoned tomato purée.