It very much depends on how old they are and how much English they already know. However, something that works for almost all ages of kids is singing along to nursery songs because it helps them pronounce the words properly and they also learn some new vocab. Another way to teach them is to read stories from a picture book out to them, Dr. Seuss book are good for the younger kids. While reading out the stories, you can show them the pictures, so that they can try to follow better. Also ask questions afterwards to make sure they understood you, if not explain again, perhaps with the aid of the pictures in the book. Lastly, it is essential to keep them engaged and provide something interactive, so that they learn while having fun. Give them fun puzzles to solve or teach them some easy grammar. If you want more tips, just get back to me ^^

Make learning English be fun, in order to exciting the children attention, such as learning English while playing, telling story on a big book, doing a little drama with English dialog, singing while to memorize the words, etc.

I think the easiest or most suitable way in teaching children with English language is teaching them first the basics like the English alphabet, then after they have learned about it, the next step is teaching them about it's branches. Always make sure that the way of teaching must suit or fit the child's understanding to avoid confusion. Thank you.