Here are a few warm-up activities you can do in the ESL classroom which require no/little prior preparation:
1- Word Groups: Using index cards write different words from different word groups, so that you will have nouns, adjectives, pronouns, verbs, and adverbs. Mix them all up and have them in the middle of the class on the floor (the desks should be in a U shape). Split the class up into two teams. Tell them the rules:
When you tell them a word group they will have to come to the middle and take a word from that group
Only one student from each group can be in the middle at a time.
You can either time them or wait until they have found all the words for a certain word group.
Each correct word with each team will count as one point, while each incorrect word will count as -1, so for example if you ask the students to gather NOUNS and a team has 4 nouns and one adjective they will get -1 point so they will get 3 points. Use the board to keep score.
2- Listening and word recognition: Write a bunch of words on the board in a random order, and also have the students divided into two teams. You will say a word and the students have to find the word and circle it. The first student to circle the word will get a point for their team. You can make this activity more challenging by writing two forms of each word: one with correct spelling and the other with incorrect spelling, so the students will have to not only recognize the word, but also decide which spelling is correct.
3- Memory game: Give each student two post-its and have them write two words on the back side of the post it. The words can either be the same word, or opposites, or a word with its picture...etc. so that they could make pairs. Then ask them to stick them on the whiteboard. After they stick them, you mix them up. Then split the class into two teams so that they will play the memory game. Any team who gets a correct pair will get a point and will get to play again.
4- Hot Seat: Also, split the students into two teams. Have them sit in a U shape. Place two chairs with their backs facing the board. Have a student from each team sit in these seats (hot seats) then write a vocabulary word on the board, and the students must help their team member to guess the word. They cannot speak in Arabic, they can give hints in English or act. The first team member sitting in the hot seat will win a point for their team. After each word, change the person sitting in the hot seat.