I recently read a post on Truehoop about Darius Miles.  He is a player who was coming off knee surgery and was trying to find his way back into the league.  In the process, he tried out for several teams.  One of these teams was the Celtics, and this is what he said:

"So far, Miles' physical condition, coming off major knee surgery, hasn't proved to be a major setback. 'When I went to training camp with the Celtics they established in me that you play hard every time you're in a game and in practice,' Miles said. 'Seeing what a championship team does made me realize that you have to work hard every time and that's what I'm going to do.'"

This again emphasizes the effort aspect of play.  If the average level of intensity is 70% for a game, the Celtics are at maybe 90% for a given practice or game.  Or maybe 85%.  Either way, it is sustained superior effort that helps them win games that they might not win ordinarily.  Conversely, some teams will be below 70% effort. 

I think teams that would be giving out minimum effort, or individual players giving minimum effort, would be players with guaranteed contracts, veteran players, and players on losing teams.  

Players with no hope yet.  Younger players with more at stake will tend to give more effort, teams doing better than the year before and with a defineable goal (either making the playoffs or winning a championship are the only two I would consider "major).  Lastly, players in a contract year.

Look at Baron Davis: Last year he played in every game because it was a contract year.  Now he has a 62 million dollar contract on losing team and hasn't played in many games while shooting his lowest percentage from the field ever.  He is giving maybe 50% effort right now.