I was sitting on a game between Staten Island and Hudson Valley and talking to a scout about different baseball things when the term makeup came up. Makeup is a widely debated topic amongst scouts (i.e. how it's defined, how to indentify it, etc.). I, personally, have always thought of it as how a player attacks the game; how badly he wants to be the best, how hard does he work, how much does he care.
Anyway, back to the story, I said to the scout that I thought a certain player had good makeup. He responded, "Why?" I told him that I had watched this player a lot, watching him take batting practice, take infield, and interact with his teammates. He responded by asking me if I thought Aaron Hernandez had good makeup before certain incidents had taken place and I told him I wasn't sure because I hadn't watched him play too closely. He then talked about how scouts will never have a full grasp on these kids and how they'll never know what the players are like off the field. He said we just have to do the best we can with it.
I disagreed. I still believe(d) that makeup had to do with how a player acted on the field. Character definitely bleeds into makeup a little bit, but only a little bit. I talked to another scout about this and he brought up Michael Jordan. Jordan wasn't a great guy off the court, and I won't go into detail about that, but on the court there was no one who was going to beat him. He was the best; he knew it; and he wanted to win more than anything else. His work ethic, his mental strength, and his want are what made him the best, not what he did off the court. The same goes for baseball players.
Sorry if these just seem like random thoughts, but I thought they were interesting.
If you would like to read more about makeup, Matthew Coller put together a real good piece about it last year on this site. You can click on his name to get to it. It gets my highest level of recommendation.