As a newly qualified FO going staight onto a medium jet I can definitely say that basic JAA training to fATPL does precious little to prepare you for the multi-crew environment.
Throughout basic training you do everything yourself - radios, nav, fly, plan make decisions. Whilst this is probably a good thing I definitely think there should be more of a bridge to the real multi-crew world. The MCC course doesn't quite cut it as it's usually 2 newly qualified pilots together for the course so the gradient is contrived / unrealistic. That goes for much of conversion training too.
I've asked the question of 'what are the qualities of a good FO' to most of the Training Capts I've encountered so far. Here are some of the responses I found helpful..
'Be supportive of the Captain'
'Make sure safety is your No 1 boss'
'Asking a question can be a better way of highlighting a potential problem than stating it in the first instance.'
'Be on time and come prepared always'
'Don't try to go for promotion by acting like the Captain. The best way to get promoted to Captain is to be a good FO.'
'Be aware of your issues as a person. If you have a tendancy to be abrassive or passive for example (we all have something), be aware of it and constantly compensate for it - keep looking in your personal mirror'.