The character influences the actions of the enchanted creature by suggesting a course of activity (limited to a sentence or two). The suggestion must be worded in such a manner as to make the activity sound reasonable.
The suggested course of activity can continue for the entire duration. If the suggested activity can be completed in a shorter time, the spell ends when the subject finishes what he was asked to do. The character can instead specify conditions that will trigger a special activity during the duration. For example, the character might suggest that a noble knight give her warhorse to the first beggar she meets. If the condition is not met before the spell expires, the activity is not performed.
A very reasonable suggestion causes the save to be made with a penalty (such as –1, –2, etc.) at the discretion of the DM.