It's all individual, and it's all Human Nature.
Of course good play stands out, and if you've personally invited anyone you automatically pay attention to them.
Field captains seem to like it if you have a positive idea of how you want to play a particular field and if it looks like they're thinking about it, you just jump in with what you think. They'll usually agree with you unless they have another role in mind for you. If everyone already knows where they want to go, or where they're most likely to go, when everyone walks the field, they don't have to wait for the field captain to tell them, they just tell him and everyone gets off the field faster, so they can walk the next one.
Part of telling the field cap. what you want to do is projecting confidence in your abilities. If you wait for him to tell you what he wants, he may have already assigned the position you play best, to someone else.
Be positive, seek feed back after a game but don't get wimpy about it. On the field, we do ALOT of yelling, nothing abusive, we just need to yell...one front player almost cried when he was telling us he doesn't like people yelling at him. He was a good player but we automatically knew that he wasn't for us. We don't yell off the field, we yell when things are going on so we're heard and understood.
Do your very best not to be the first elimination...yet play hard...nuf said.
Make sure the team captain knows how to contact you, and after practice, during the week, make a point of calling the team captain and asking him directly what he thought of you. Don't mince words, you don't want him wasting your time, just as you don't want to waste his time.
have fun.
Ray