In order to pass ordinances and commission public works projects after becoming mayor, you must increase your approval rating around town to the maximum 100 percent. There are several ways to increase your approval, and you'll likely need to accomplish them all.

Action	Approval Points
Change town flag	3 points (awarded once only).
Change town music	3 points (awarded once only).
Donate fish/bug/fossil/artwork to museum	7 points (awarded once only).
Fish out trash from water	1 point each (repeatable).
Introduce yourself to villagers	1 point per villager.
Perform errands for villagers	3 points per errand (repeatable).
Playing the game	Up to 3 points per day.
Post on the bulletin board next to train station	3 points (awarded once only).
Pull weeds	1 point each (repeatable).
Sell anything to Re-Tail	3 points (awarded once only).
Sell junk/trash to Re-Tail	1 points (repeatable).
Send letters	1 point each (repeatable).
Upgrade the tent you start with to a house	20 points (awarded once only).
Water flowers	1 point each (repeatable).