In the API 2.1, controls are added to the map automatically when it is created. By default, the 'mediumMapDefaultSet' standard set of controls is added to the map (see the example).
To add the desired controls to the map, a list of corresponding keys can be specified in the controls parameter when it is created. The controls can also be added through the Map.controls map field, using the "add" method.
You can specify individual controls, or a set of them. If you want to display the map without controls, pass an empty array  in the "controls" field.
A list of the available controls can be found here.