Either that, or to actually be able to read the 9-11 Comission's Final Report...
But Think Progress has summarized the facts on this aspect of things for you:
1) Bush received intel briefing on Aug. 6, 2001 entitled “Bin Laden Determined To Strike In US.” The briefing specifically warned to “patterns of suspicious activity in this country consistent with preparations for hijackings or other types of attacks,” particularly targeted at New York.
2) CIA Director George Tenet briefing Condoleezza Rice and other top administration officials on July 10, 2001 about a specific urgent and looming threat from al Qaeda.
3) An FBI agent in Phoenix sent a memo to FBI headquarters on July 10, 2001, which advised of the “possibility of a coordinated effort” by bin Laden to send students to the United States to attend civil aviation schools.
David Neiwert at Orcinus covers this in a more detailed fashion.
At the very least, Bu$hie's inaction prior to 9-11 was comparable to his inaction in response to hurricane Katrina. The motivations behind the inaction are a matter of conjecture. Whatever Dear Leader's motivations were, there is no doubt there were and are unscrupulous associates of his that seemed quite ready to take advantage of the chaos to further their own agendas.