Lpc2000

I am trying to get a LPC2106 to talk to a PCF8574A chip which is 8 bit
I/O expander. I cant seem to get any thing to happen when using the
I2C example posted in the files section here.

Do I need external pull up resistors on the scl and sda lines?

What initiates a transfer? setting the STA bit in I2CONSET? 

Would it be better to use an interupt driven approach? or just
directly control it in my main loop if I know exactly when I want to
recieve data? 

Thanks 
Josiah