It's a rotating assignment - depending on how the detailers run their company they may ask for volunteers (it's always good to volunteer...shows you are willing to take charge, step-up, etc) or they assign it to people. Obviously you can't be a complete screw up b/c it's a duty not taken lightly, you have to guard your company guidon take care of it don't lose it, etc...it's not so much a leadership position but it's a good position to have, they may hold it for a week or a few days depending on each company. Same thing will go for squad leaders, now this is a leadership position. these types of positions are usually selected by the detailers - it's a test to see how plebes handle their squad/squad mates. they are responsible to make sure they get to where they are going, make sure everyone is in the right uniform, etc...