@Sarah84Chris77this is a quick copy paste of a guide of sorts I received a while ago.
In the advanced search content search form at the bottom, select 'Extended Query Search' and then in the 'search for' field enter:
@content keyword @storyTags tag
replace keyword with whatever words you want to search for in the text and replace tag with whatever tags you want. You have to spell the tags as they are spelled in the category search page (although I'm not sure if it works in with the categories that contain a slash (like Ma/ft for example)
You can even do the boolean stuff in there. Example:
@content saturn -pluto @storyTags Science Fiction -Aliens
The above:
Search story text for 'Saturn', but exclude any text that contains 'Pluto' and tags contain 'Science fiction' and exclude any tagged with aliens.
it likely hasn't changed that much since then. I think the only thing that I find frustrating is that you can't use Boolean words like NEAR. This is an old holdover from my time using the Altavista search engine from the days before Google.
I don't have a proper list of included and otherwise excluded list of operands but I have a personal preference for word based selectors over symbols.
have fun exp;erimenting.