02 alero 3.4L
 

My 02 Alero 3.4L has an annoying P0420 Catalyst System Efficiency Below Threshold (Bank 1) engine fault. As far as a visual of the cats which will just look all rusty anyways, what would be the best check points to start trouble shooting?
If anyone has had this issue on their Alero and fixed the problem, id like to hear how you solved it.

for a start, which side is bank 1?
Thanks