English teachers who are asked to teach young learners for the first time often ask "How should I teach them?"

My answer is - Don't.  

??? 

That's right - Don't teach them at all. Young children learn on their own without being taught. Expose them to English by speaking to them, singing, playing games and reading stories and they will absorb the language naturally. Explanations will bore and confuse them, and are unnecessary. 

Now for some more specific ideas: 

Speak - Young children are very tuned in to body language, facial expressions and voice intonation. Unless you are giving complicated instructions, speak English and use gestures to make the meaning clear. They will quickly become accustomed to hearing English and recognize common words and phrases. 

Sing - Songs are an excellent way to learn and remember language along with its natural rhythm and flow. Singing should be active - add movements, hand motions and props rather than just watching videos. Make sure the lyrics of the songs are simple, repetitive and suitable for EFL students. They don't have to understand every word, but don't burden them with words like "merrily" and "water spout". This is why I started writing my own songs. 

Play- If you play games that they already know, it will be easy for them to understand instructions in English, allowing you to use very little L1 and making them feel more comfortable by creating a familiar atmosphere. Use games in which the children repeat a few words or sentences. Some popular kindergarten games I use are Knock-Knock-What's My Name, Telephone, What's Missing, Red Light/Green Light and Hot/Cold. 

Show them - Do any activity they like, but do it in English. Whether you dance, draw, cook or throw a ball, if they can see what you're doing while you speak to them they will understand and pick up new vocabulary. 

A few basic rules to remember:

• Keep them active. Kids need to move.
• Be friendly and patient. Everyone learns at their own pace.
• Children learn by hearing, seeing and doing.
• Avoid translating whenever possible. Use props, pictures or gestures instead. The disadvantages of translation can fill another blog post.
• Make it fun. They more they enjoy English, the more they'll learn now and in the future.

References:

Giving children non-verbal clues about words boosts vocabulary

How exposure to a foreign language ignites infants' learning

Critical period effects in second language learning