If the plural doesn't find what you want, try the singular, or vice versa (women, woman).
Make sure you don't put any extra spaces in the search.
Make sure you have things spelled right. This might mean US or UK spelling, different authors use different spellings.
Don't search for something obvious, like "woman", or you'll get so many matches, it'll be useless.
Don't try to explain what you want, just type in the words to look for, and Sandra will find the files that have those words, all together, in that order.
Try using phrases like "head scissors" as well as words like "headscissors"