When teaching students who have no basic knowledge of English, get a basic understanding of their language(s). This is because you will need to know the elements of both languages in order to translate effectively. By studying a few words of the students' native language(s), you will get a grasp on its vowels and sentence structure.
Start teaching by explaining the most significant part of any language--vowels. Vowels vary from language to language and can be very difficult for a non-native English speaker to pronounce. Sound out the vowels in a manner that your students can follow. Allow the students to study the vowels and give them an oral test.
Flash cards are an effective way to teach a language. On one side of the flash card, write the word and/or the picture of the object you are asking your students to learn. On the other side write the translation in the students' native language(s). One by one, hold the flashcards up in front of the students and tell them to pronounce the English word.
There are also many books available at your local bookstore that you can recommend to your students. "English for Dummies" is a good book for moderate English speakers (see Resources). Also recommend a language-to-language dictionary (e.g., Spanish to English or Japanese to English).
An effective way to teach English is by using interactive audio tapes (e.g., Primsleur English), videos and software. The Rosetta Stone series is an easy-to-understand language-learning software (see Resources). Interactive tapes allow a person to hear exactly how a word is meant to be pronounced. It helps when the tape specifically orders a person to repeat the word several times. Stopping the video/tape several times will allow listeners to understand what is being said more effectively. After the tape/video is finished, it helps to give a quick quiz that will cover most of the tape/video's contents.