Usually, when said phrase is used, it is followed by a near-endless spree of other quotes such as:
1.) Psh, I don't even know.
2.) Aw hail naw.
3.) Aw hail naw, cracka.
4.) Mmm hmmmm!
The phrase "I don't even know" is best used in the classic "I don't even know" speaking tone, which may only be properly "voiced" by either a colossal, Japanese monster, a small cat/kitten, or a constantly hyper-active younger brother.
"Psh, I don't even know!"
"What's going on tonight, bro?"
"I don't even know, man."
((When in a conversation and an awkward silence comes up))
"Yeah, well, I dont even know."