Understanding varies by country; some places expect gratuities, others include it in the bill already. When dining in Japan, offering a gratuity is often seen as rude.
Pro Tip 2/3
Service Appreciation
Gratuity is given directly to service staff to show satisfaction beyond the payment for the service. The concierge was so helpful, I left a gratuity in thanks.
Pro Tip 3/3
Customary Amounts
The usual amount ranges from 15% to 20% of the bill, but this can depend on service quality. Our bill was $100, so we added a $20 gratuity.