Restaurants: 15% to 20%, with 20% being the norm at high-end restaurants.
Taxis: 15%, or round up to the next dollar amount.
Hotel Porters: $1 per bag, but at luxury hotels such as Four Seasons properties, $2 to $5 per bag is the norm.
Hotel Concierge: $3 to $5 for a simple service, such as arranging airport transportation. For a more complicated request, such as a hard-to-score reservation, tip $20 and up.

Restaurants: Service charges are included in most meals, but add another 5% to 10%. If no service charge is included, add 15% to the bill. Taxis: 10%.
Hotel Porters: The equivalent of $2 per bag (or about 1.50 euros)
Hotel Concierge: $2 is enough for easy requests, but this amount should increase to $30 or more for special requests, such as getting an after-hours tour of the Louvre.

Asia: Japan, China and Hong Kong

Restaurants: In Japan, it’s considered an insult to tip for anything. In China, 3% is the norm, and in Hong Kong, 10% to 15%, if it’s not already included in the bill.
Taxis: In China, no tip is necessary. In Hong Kong, round up to the next dollar.
Hotel Porters: $2 to $3 per bag at high-end hotels.
Hotel Concierge: $3 to $5 for basic requests such as dinner reservations. Incrementally increase the amount based on the complexity of your request.

Asia: India

Restaurants: If it’s factored in, leave a few dollars extra. If not, leave 10%.
Taxis: It is not necessary to tip.
Hotel Porters: The equivalent of $1 per bag.
Hotel Concierge: $2 for easy tasks and up to $20 for more intricate requests, such as arranging Mumbai’s top jeweler, Neelam Kothari, to bring her latest collection to your hotel room for a private viewing.

Restaurants: In most cases, gratuity is already factored in. If not, 10% is the norm.
Taxis: 10% in major cities.
Hotel Porters: The equivalent of $1 per bag.
Hotel Concierge: $2 for simple tasks. Increase the amount based on the complexity of the request, but usually there’s no need to exceed $20.

Australia/New Zealand

Restaurants: For fine dining, 10% to 15% is acceptable. Otherwise, a service charge is almost always included.
Taxis: Round up the fare to the next dollar amount.
Hotel Porters: The equivalent of $2 per bag.
Hotel Concierge: $2 for each basic task, such as arranging transportation, and up to $50 for harder requests, such as scoring tickets to a sold-out opera at Sydney Opera House.

Restaurants: For fine dining, 10% to 15% is acceptable. Otherwise, a service charge is almost always included.
Taxis: Round up the fare to the next dollar amount.
Hotel Porters: The equivalent of $2 per bag.
Hotel Concierge: $2 for each basic task, such as arranging transportation, and up to $50 for harder requests, such as scoring tickets to a sold-out opera at Sydney Opera House.

Mexico/Central America

Restaurants: 10% to 15% is expected.
Taxis: Round up to the next dollar amount.
Hotel Porters: The equivalent of $1 per bag.
Hotel Concierge: For simple tasks, $2 per request is enough. For more complicated ones, increase incrementally based on the task–up to $20.

As printed in HRI – Hotel & Resort Insider