Use fresh ingredients whenever possible; fresh spinach and garlic make a notable difference. If ricotta is too dense, whip it lightly to make it creamy and easier to mix. Experiment with different herbs like basil or thyme for flavor variations. Avoid packing the meatballs too tightly to keep them tender and juicy. Store any leftovers in an airtight container in the refrigerator for up to 3 days. For longer storage, freeze meatballs without the sauce for up to 2 months.