Most students enjoy playing games from time to time, even adults, who after a long day's work need a bit of relaxation. As I mostly teach young learners, I will be focussing on using games with them, but you could use the same principles with more mature students. One of the important things to decide before you play a game is whether the objective is just to play and give students a break, or if you want to practise a specific set of vocabulary or grammar point. With children I usually involve some vocabulary practice, but it can be a good idea to allow older students to play as a break in the lesson or as a reward for working well. There are many traditional board and card games that you may have at home which you can use in class.
You will need a set of cards with pictures on. There are some nice sets available for children that have pictures of animals that are split into two or three cards. This makes it into a kind of jigsaw puzzle. With a group of young children for example aged 5, deal the cards until everyone has the same number, if there are any left over, keep them for yourself to demonstrate and start off the game. Place one of the cards on the floor an ask the children if they have a card which matches it. If so they place it in the right position. When you have placed all the extra cards, say the name of an animal e.g lion and the children that have the lion come and place their card on the floor. The winner is the child who gets rid of all their cards first. Afterwards, you could play a pelmanism game where all the cards are spread out face down on the floor and the children take it in turns to turn over a card. When they find a match, they form the animal and keep it.
This can be done with almost any set of cards or even dominoes. Games traditionally played in small groups can become whole class activities.
Games such as Monopoly, Ludo, Scrabble, Snakes and Ladders or Cluedo can all be played with the whole class by dividing the students into teams. I have a large floor board game which is called The game of the goose. It is a traditional board game in Spain. The one I have is based on a national children's TV programme. It has giant counters and a giant dice, making it ideal for the whole class to play. What I usually do is show the children a flashcard every time they throw the dice, and they can only move forward if they say the word correctly. If they are a bit older (7-8) I ask them questions, sometimes based on pictures or objects e.g What is the boy doing? How many pencils are there? etc. You could use this strategy with Snakes and Ladders or Ludo. Monopoly and Cluedo are more complex games and require lots of language, which you will need to prepare students with before playing. You can grade the language provided depending on the level. Scrabble can be played according to the rules, or you could just use the letters. A very popular game in my school is Combiletter, which can also be played with Scrabble letters, where the letters are placed face down in the middle of the table (or floor) and are turned over one by one. When a student sees a word can be formed with those letters, he/she says "Stop!" and forms the word, which the team keeps.
Other children's games such as "Guess Who" can be very useful when teaching parts of the body or "has got". Playing such games makes the lesson much more fun and motivating for the children, although beware of using them too much! Young Learners will get used to playing games and will demand to play every day, something which should not always be allowed. Make sure that your learners do all the work before they play, or just let them play occasionally as a treat. When the games are to practice a certain structure or vocabulary, tell the students this so that they know why they are playing. If you do have the odd student who doesn't like playing games and feels that they are not learning if they are playing, explain the reasons why they are playing and what they are learning/practising with this.
Generally, using games regularly as either a way of learning and practising or as a break from the routine of the course book, can be a postive way in which you can reward your students for their hard work, and get a few brownie points in the process!