Ino looks to be the leader of the team in most scenes, but if there is a leader it's really Shikamaru. He's the one who decides when the team should go for it, or run away. Typically the latter, but oh well... He also is the one that plants little suggestions in his teammates brains, that is if they have any. But the real reason Ino looks as if she's the leader is probably because Shikamaru's mother is a very bossy woman and he's used to having a female character around that's on the strong side. But he can put his foot down if he needs too.

But a leader? Shikamaru, the laziest ninja who has no real plans to amount to anything (yet the only genin promoted to Chuunin from the Chuunin exams, even though he lost... Well, not lost but forfeited when he ha the advantage.)? Because he is a natural at leading. Some have it, some don't. Even the weakest of ninja's can become great by using their comrades (and themselves) in a strategy that none by themselves could think of. An example of this is Quatre from Gundam Wing who is the weakest pilot, but one of the more feared because he is a strategical genius who can not only make all the other pilots work together but employ them so that it works when they work together. Understand the allusion? Well, I'm not very good at explaining, so that above sentence is all I can give to work with. ^_^