Most Samoan people will attend a church service in the morning before gathering for a traditional family lunch known as "Toanai". If you are travelling around Samoa on a Sunday, there is an expectation that you will behave quietly and move slowly through villages.
Many resorts and restaurants will stay open on Sundays, but most activities, sites and attractions, fuel stations other businesses are generally closed. Some grocery shops and food markets open first thing, before church, for locals to stock up for their family meal later in the day.
You're welcome to attend church services, which are often led by a beautiful choir singing. Ask at the church or your accommodation provider for service times and details. Visitors to a church service should dress modestly and women are encouraged to wear a lavalava (skirt) to cover their knees and a top that covers their shoulders.
The sale of alcohol is prohibited on Sundays except in hotels and restaurants.