So here's what you do.
Click on the little beetle type thing in the bottom right of your browser (I'm sure you've already done this). This has to be done before any page loads take place and once it is open, leave it open throughout your process.
AJAX requests show up as either POST or GET with a URL, status, and time (in ms or s) next to them. To view the detailed ajax request (parameters being passed and response being received) just click on it.
If you're unsure of what you're seeing, just click on the bottom of the firebug window (in a blank area) and drag your cursor so that everything is selected, and then you can copy and paste it here.