Use ground beef with about 15% fat for juicier meatballs or ground turkey for a leaner option. Breadcrumbs help bind the meatballs and keep them tender. Fresh parsley brightens flavor but dried herbs can be substituted. You can form meatballs a day ahead and refrigerate. For extra flavor, sear meatballs before slow cooking. Adjust sweetness by adding more brown sugar or honey. Use a 4 to 6-quart slow cooker for best results. Variations include adding chili flakes for spice, using different meats like lamb or chicken, vegetarian options with lentils or chickpeas, and gluten-free breadcrumbs.