Being an FO is what you make of it. Once you make it through training and IOE you have two basic courses you can take.

The first one is pretty easy. You can sit there and watch the world go by. Do your walkarounds, fly your legs, talk on the radio once in a while and go home. This easy way will probably cause you the most headache in the long run.

Better yet, use the time wisely. You're training to be a captain. I like to get involved. If not making the decisions, I like to pick the captain's brain on why they do what they do. Why go left around a storm rather than right? Why did you add the extra 1000 pounds of fuel? Look at the performance books, can you go to 390 at this weight? The captain's getting a cup of coffee at starbucks, the gate agent wants to start boarding but the FAs aren't ready.

Make a choice, then ask what the captain would do if it's their leg. They may override you, but there is likely a good reason. Chances are they have more experience than you, that's why they're in the left seat. Experience is everything. The more you have, and the more you're involved in only means you have more to fall back on when you move to the left seat. The SOP only says so much.

Every captain I have flown with has been more than receptive to this stuff. You'll be ready to go when it's your turn to upgrade or when you go through recurrent.

It's kind of hard to explain that feeling of responsibility. It was downright frightening the first time one of my students looked at me and with that "now what?" look. They're relying on you for your experience and you don't have much. Now, multiply that by 19/35/50/70 (I don't really care what the number is, 1 is enough) and you sort of get an idea of what you're dealing with. I don't take that lightly and I hope that when it's my hide on the line I make the right choices.