Making good, well-researched lesson plans is imperative in order to effectively teach learners of English as a second language. As you develop as a teacher, the time required to prepare for a lesson and make a lesson plan will become shorter and shorter. A new ESL teacher, however, should be spending an hour or more to prepare for a two-hour lesson.

Detail
Novice teachers especially should make their lesson plans as detailed as possible so that they are always aware of what they should be doing next and why. A lesson plan prepared in this manner will give you something to refer to during the lesson and can act as a valuable crutch. Even if you find that you actually refer to this lesson plan infrequently when in the classroom, the process of making it is invaluable and it is far better to have too much detail and content than too little.

Timing
It is important to work out roughly how long each activity will take. This will allow you to plan when to introduce new activities and to calculate how much practice of a language point each of your activities will give the students. In this way, you can balance your lesson appropriately so that you don't end up spending so long on a grammar point, for example, that students get little time to actually produce any language.

Three Basic Stages
In general, a good plan for an ESL lesson will contain: a presentation section, near the start of the lesson, where you plan to introduce new language; a practice section where students can practice using the new language in a controlled activity in order to develop accuracy; and a production section where students are free to use new language in a less controlled activity in order to develop their fluency. These three stages form the basis of most English language lessons.

Adapted and Used Again
You can use a detailed, carefully written lesson plan again and again for similar classes although you will, of course, need to adapt it to suit the needs of your particular students. This process of adaption is valuable in itself as you can recall parts of the lesson that went well and reuse them while altering or removing activities and exercises that were not effective. In this way you can both cut down on the amount of time you spend preparing lessons and also improve them.