For level A1-A2:
Ask "What do you eat for breakfast/lunch/ dinner?" Show pictures of breakfast/lunch/dinner foods. A good resource book is Longman's Photo Dictionary (ISBN 978-1-4082-6195-8) In section 8 you will find pictures of food. Ask each student to tell what they eat for each meal. Then introduce foods that weren't mentioned. Ask them to write down what they think people eat in 3 other countries. Pair the students up and have them tell their partner which countries/ foods they wrote down. Students report to the class about their partners choices. Hand out cards with different foods on them and ask students to walk around and ask "Do you eat______for breakfast/lunch/dinner?" If the student being asked has the matching card they answer yes and give the card to the student asking the question. The student who is the first to match all of his/her cards wins the game.
For level B1:
Begin a conversation about what students normally eat for breakfast/lunch/dinner. Ask if they shop everyday. Ask students where they buy their food. Then give them copies of pages 84-87 of English the American Way (ISBN 978-0-7386-0676-7) Ask them to look at the words in bold first and tell in their own words what they mean. If there are words that no one knows, tell them what they mean. Then have them read the article out loud. Discuss the contents briefly and then tell the students they will hear a short dialogue between a woman and a farmer at a farmer's market. Play track 26 and then ask the students to summarize what they heard.
Tell them they are going to then learn phrases dealing with eating together. In the book Conversational American English ( ISBN 978-0-07-174131-6) # 423 begins with phrases used to tell someone you are hungry. Have students read the phrases orally, then tell them to choose a partner and write a short dialogue about food/hunger. Then have the students read their dialogue to the class.
In the book 101 American Customs (ISBN978-0-8442-2407-7) you can introduce students to typical American 'table manners'. Begin a discussion about good and bad manners in different countries. One possible activity is to give students a country and have them find out about good/bad manners and report to the class. Another variation is to have them tell the class about how to prepare their favorite food.
For level B2:
Begin the conversation by asking students what traditional foods they eat on their holidays. Have them tell what ingredients are in the food. If they don't know the English names, google them. Then put the students in pairs and give them a holiday. Tell them they are to research the history of the traditional foods for that holiday. Give them 30 minutes to do this. Then have them report to the class their findings.