Best way to see what a 1st officer does is to see it. The site below has videos of airline flights, taken from specially placed flightdeck cameras (and others) and will give you a good idea of exactly what goes on frompoint of view of both pilot-flying and PNF. Both pilots talk you through all they do and show you round cockpit etc during flight.
http://www.itvv.com/details.asp
The 'platinum collection' ones are far better as they use more cameras and are better produced. I got the Go 737 & BMI Fokker 100 ones and can recommend both