Thats what i love about IOIs, too basic, too many times when you cannot distinguish them apart from real/fake. Look for other things.....sure fire signs that are even better that IOIs cause you cannot fake them, they will be genuine considering the subject is sober
Clumsiness
Dumbness/unique acts towards you.
Womanly Acts
If some trick is truly interested she'll be dropping a few acts from 1 of the terms above.....why? Because with those you can tell there is "obvious mental stimulation" going on. Clumsiness can be caused by preoccupation of the attention span, therefore not acknowledging typical things you would normally determine. I've seen some chicks tripping or randomly bumping into shit out of no where. Walked up to order some food, bitch trips on the carpet(wasnt even sticking up or a hazard either), I laugh, she hits me. Walking in the mall, bitch trips on the flat marble floor while paying attention to what i was saying.....blamed it on her sandals. And no these chicks didnt have gimp legs either

hhahaha.
Dumbness or wtf moments...usually if your aware youll notice a few things she does that just does not seem right. That brings upon the question of Why? Why did she do this? Example: I had this chick i was unsure of(mainly because I was in a case just like yours, couldnt call it just over the basic IOIs). Had to take this chick around(this was at work

) and upon departure she was lingering around when she did not need to be. Typically a person who has no interest will be on the move, moving right along to their next place to be or place to go... no need to be around a certain area if there is not a reason...savy? Sort of those unique moments that can help you distinguish between special SPAM towards you vs. Its just the way she acts towards everybody.
Womanly Manners: My favorite thing to look for. A lot of pros wouldnt classify this as a sign but use SIMPLE LOGIC(the simple things) it ties in perfectly. This can be womanly care, cooking you food, basically WILLINGNESS to Oblige to your agenda! Some chick is not going to waste her effort towards you knowing its just going to waste(watch it there, bitches trap like this as well). You can simply judge though if shes doing it out of spite of you or because she wants something from you. Why does this happen? Becuz she wants to demonstrate shes truly a woman and that she can provide her half of relationship 50/50(instincts).
And just as proof, flip this around making it the Male to the Female. Ive been clumsy in the presence of girls of interest, having quick blank mind moments. If i like the bitch Ill be flirting with her...and if i really want to reel her in demonstrate my value as a suitable Male.
The answers are right in front of you, believe Nature, trust it! Good luck