I've been struggling with a relatively minor issue regarding how the members of squads are placed. If I order a squad of marksdwarves to defend my fortifications, often some of the members of the squad end up deploying outside of the fort. Similarly, if I place my melee squad in a hallway between two fortified rooms, some of the squad members may choose to wait inside the rooms (even if the rooms do not have entrances nearby).
Here's what I've observed about the issue:
The squad leader always goes exactly where the squad is stationed. The other dwarves in the squad are always within a few squares of him, but they completely disregard anything in the intervening space (walls, channels, etc).
Here's a screenshot of a two member squad, where a marksdwarf choose to position himself outside of the fortifications (and across the (currently) dry moat from the Mayor, his squad leader:
You can also see two members of the melee squad in the hallway below. When the other two members of the squad show up, it is a good chance that at least one of them will stand behind the fortifications to the north or south (and while you can't see it, the entrance to the room to the south is a long walking distance from the hallway). Melee troops there are entirely useless to the squad, which is placed where it is for the purpose of holding the hallway.
Edited to try to fix image... (x3)
[ May 19, 2008: Message edited by: BlckKnght ]