Summer is notorious for having underaged hootch makers coming on. Usually you can tell, by how they write, how they phrase things, and what they're asking about. And yes, 99% of the time, if the person is asking about fermenting table sugar with bread yeast, it's usually a red flag for me.
The first thing I do then is look at the OP's profile, a surprising number of underage posters do NOT lie about their age. If they are open about being underage, I report them, and if I am suspiscious, I report them too. Just click on the
report post button next to the quote button, and write "Hootch thread" or "Underage Poster" and most of the time the mods will check it out.