For example, I'm going to take a basic eastern MMORPG.
Possible Actions:
Grinding
Farming
Quests
In-Game events
Organized Play (Team Play)
Organized wars
Socializing/Community building.
Possible Motivators:
Power
Greed
Competitiveness
Expression / Build creation
Exploring
Socializing
Then figure out what actions are "fed" by what motivators. That is, which actions will satisfy particular wants and desires of your players.
Farming
Motivators: Power, Greed, Competitiveness, Expression
Questing
Motivators: Power, Greed, Competitiveness
Grinding
Motivators: Power, Greed, Competitiveness
Organized Play
Motivators: Socializing, Power, Greed, Competitiveness, Expression
Socializing/Community building:
Motivators: Socializing.
Then figure out which action is rewards some motivations *the most* in your game so you can refine your list down. In most games, Organized play isn't the best way to satisfy power leveling. However, organized play can be the only source for some hard to acquire items. In this case, farming and organized play both satisfy greed the most in different ways.. so our refined list looks like..
Farming
Motivators: Greed
Questing
Motivators: None
Grinding
Motivators: Power, Competitiveness
Organized Play
Motivators: Greed, Socializing, Expression
Socializing/Community building:
Motivators: Socializing.
Now you have a pretty good idea of what is going to be the dominant actions that are going to be taken in the game. If you have a better idea of specific actions in your game, you can further refine this chart to determine what actions a potential player will do. Further refinements to this list can include: availability of the various actions you can take (for example, if there are only 3 quests in the entire game then questing can't satisfy its motivators because it's not available all the time). You can also figure out if you need to design more actions to satisfy base motivators, like specific quests designed to attract players who are driven by say, greed and socializing.