What are some signs that a person might be a genius?

they're me 

An ability.  Usually people are not geniuses at everything.  Even Leonardo DaVinci, talented as he was, did not know all.

But if you have only one ability and drool and can't do much else, you are an idiot savant.

If you just drool like an idiot, you are promoted to Attorney General.

Dum'b ,,,Blonde air I fink....:(X)

Unfortunately, there is no scientifically precise definition of a genius, and the question of whether the notion itself has any real meaning has long been a subject of debate.   (Wikipedia)

Listening to someone talk or reading something one has written usually indicates intelligence, but that doesn't answer your question.  (But I'll settle for intelligence.)

They aren't on the Internet.

They are absent minded. 

They are terrible drivers

They can't even walk across the street safely

Most geniuses are atheist 

I'm hoping lots of meaningless sex counts.

I could use the grant money .

The person announces it in public interviews and tweets. That's the best way. For sure.

exceptional love of, attraction to and indulgence in intellectual subjects and ability to make significant contributions to the relevant fields.

original thinking -
i.e. coming up with discoveries that change the way humans understand physics or some aspect of how the world functions
or inventing new substances, processes, tools or technologies
or inventing new modes of expression in the arts

Their name starts with J.