One addition.

Investigate the properties of your items. The more you know about your items, the more options you have to use them, often in unusual ways. A spoiled egg is trash. But if you figure out how it smells, you can guess it releases sulfur (hydrogen sulfide) and can be used in the spell that calls for brimstone.  The hosts noted that they couldn't collect water in the hunter's lamp earlier, but they couldn't do it before they had read the spell book and figured out how "falling water" could be used.