I don't know if you've gotten around to it or not but I'd recommend Anthony Bourdains book Kitchen Confidential. Its great for people just starting out and great to reread as time goes by.
Always keeping a cool head is definitely number 1, when the chef or middle guy starts to lose it the line can feel it and quickly lead to disaster. Learn to let things go, it does get intense on the line at times, there may be a dispute amongst guys on the line, someone messing up/slowing things down but you need to quickly take action to fix the problem and then act like nothing ever happened to keep their morale up. "You know what you did wrong? You know how to avoid it? Good, now don't do it again." and right back to smiles and good times.
As a line cook in general its good to know your place, don't go trying to change things or be an "artist" its the chefs menu, execute it as best you can as consistently as you can. however, don't be afraid to discuss ideas with the chef once you kind of proved your value/knowledge on the line.
Consistency... consistency is everything. You need to be able to turn out the same dish, the exact same way you've done it all previous 150 times that night.
Cleanliness, organization, take responsibilty for your station and take ownership of it and your "meez." I've gone and bought several pieces of my own equipment just to have my meez precisely how I want it, and so that no one on the line will need to borrow anything of mine. This doesn't mean not to look out for other stations, the line is a team, but remember your station comes first, and you don't want anyone having to get you out of the weeds, you wanna be the guy getting everyone else out of the weeds. Make a list of everything you need and if there's downtime instantly restock it. I mean EVERYTHING.
Its fine to talk with the guys on the line and make it fun, but remember the priority is good food, when you get an order in stop whatever bullshitting you were doing and get on it. Food first, over everything.
learn spanish.