Well the easiest thing to do is to check your fridge at the end of every week, and take inventory. Chop up all the leftovers and combine. Use up whatever you can before heading to the grocery store to restock with fresh items.
(Adapted Southern Living and an article they just featured on using 'leftovers').
Ends & pieces of any veggie you like, chopped:
-Red onion or green onion
-leftover rotisserie chicken or extra chicken breast
1. Wash your hands.
2. Boil 2-3 cups pasta unless you have leftovers from a separate meal.