My "red flags":
Target numbers. Hate em. Think its an incredibly lazy, inelegant solution for a task resolution mechanic. I can hande them if they're kept on a scale of 1-10, but other than that, no thanks a billion other games have already done it, and I didnt like it then.
Anime/Maga artwork. Its not that I have anything against that style of art, and I even own a few anime films and series. But it doesn't inspire me, and 9 time sout of 10, if its done by an American artist, its just an excuse for not learning how to draw.
Funky names for the GM (Storyteller, hollyhack Diety, etc). Or the GM's duties are redistributed among the players, and then the designer redefines the term GM to fit their game.
Character sheets that cannot fit on an index card. Clear sign of rules glut.
Nonstandard die types. Because fuck you DCC, thats why.
Its a game Gleichmann likes. Because, my god, any game that he enjoys has to be crap on a stick based on his complaints.