If someone is generally seeking attention, clowning around, being funny, acting ridiculous, etc. it will probably get my attention. Not necessarily though. For some reason the way Fe demonstrative types do this generally just irritates me rather than being amusing. (My general theory on this is that the demonstrative function is used selfishly, rather than for others.)
Flashy clothing and any attempt to seek attention through one's physical appearance or displays of wealth and status are a definite turn-off -- but my idea of what is flashy probably includes way more than it does for many people (including @
Chae).
The other way is if someone starts dropping some knowledge that I didn't know already...instant attention. But that's a lot more difficult to find.