Before and After the Meal by Molly Hakes
First introduced in Chapter 5, the phrase itadakimasu is used when receiving anything in Japan. “I humbly receive” is the literal translation, but it has connotations of various underlying feelings. Used sincerely, it is a sign of respect towards the gift-giver, reflects a reverence for the food, and also shows an appreciation for the work that went into preparing it.
Most often uttered before consuming a meal or snack, it is also used before accepting even a tiny piece of chocolate. At school lunches, once the servers have dished out everyone's portions, students (as well as teachers and staff) say itadakimasu before digging in.
You are not expected to tip your server or cab driver. Most Japanese people are aware of the custom and there is even a katakana-style English word for it, chippu. However, the practice of tipping is rare to nonexistent in Japan.
On the flipside we've got gochisoo sama deshita. When the meal is over, belts loosened and plates scraped, gochisoo sama deshita is a way of saying “thanks for running around and working so hard to prepare this meal.” Put more simply it translates to, “It was a feast.” Even if it was just tea and crackers, it is polite to use this phrase at the end of the meal.
Gochisoo sama desu, the present-tense version, is sometimes used in place of itadakimasu. This variation can be heard most often in situations where what was received will not be consumed in the presence of the gift-giver. For example, if someone brings back cookies as a souvenir from a trip, it is fine to use gochisoo sama desu when accepting the treat. If you plan to pop it into your mouth right away, throw in an itadakimasu before it touches your tongue, at least.