It's been a while so I might be off, but I think the general rule is wherever you shoot her, she'll put her hand on the spot (edit: NVM, just shoot random parts and take note how it reacts, plan your path from there).
There are different ways of downing the bosses, actually. If you've already beat the game and you wanna see some badass stunts, check out the time attacks on youtube. They do some crazy shit - like run straight towards the final boss (while being shot at), and pulling some crazy jumps using the game physics... fun stuff.
Anyway, this is easily Sony's game best for me. While I partially regret paying for the PS3 (more stuff on the 360 I want atm), it'll all change as soon as Team Ico shows up. I'll always remember the fight with the first colossus, with no battle experience at all so my first thought was, "I'm supposed to fight that thing?"
