Days of the week are generally taught very early on in ESL courses so it is important to incorporate recently studied material into your lessons without overwhelming your students. For this example, it is assumed that students have studied ordinal numbers (1st10th), subjects (math, science, art, music, etc), and the simple present tense.
How To Proceed

1
Warm up
Use the start of class as a review of the previous lesson. Students will feel more confident in a class if you start out with material they have already covered and it will also prepare them to use that same material later on in the lesson. 
2
Introduce – Days of the Week (vocabulary)
Write the words Sunday through Saturday on the board one at a time demonstrating pronunciation and drilling as you go. Practice the days of the week in order using choral repetition and then challenge your students by pointing to words out of order to test their pronunciation as a class and individually. 
3
Introduce – Days of the Week (comprehension)
Tell students “Today is ~” using whatever the day of the week is. Tell them that they go to school on Monday, Tuesday, Wednesday, Thursday and Friday or that they study English on Monday and Wednesday. Use several very basic examples to give students an idea of what these words might mean. Ask students for the meaning and translation of each word. It should be easy once they get started. 
4
Practice – Days of the Week
Do an activity that gives students lots of practice with the days of the week. A card game such as Go Fish with days of the week cards would be appropriate to play in groups of three to four. If using the game Go Fish simplify the dialogue so that a student only has to look at the person he is asking for a card and say the day of the week while the student being asking for a card has to say only the day of the week as they hand over the card or “Go Fish.” 
5
Practice  Review
In order to get students warmed up for the next step where they combine their new vocabulary with previously learned material, conduct a review activity. A good game to practice listening, reading, and pronunciation requires only a set of flashcards for each group of students. Ideally groups should be three to five students. Since there are only seven days of the week, perhaps combine days of the week with a review of ordinal numbers, for example 1st10th, and a list of subjects they study at school. Once each group has a set of cards, ask them to spread the cards, face up, on their desks. Explain the activity and begin. You will say a word aloud and the first person to repeat the word correctly and slap the corresponding card gets to keep that card. Repeat until all the cards have been gathered. Whoever has the most cards in the class should read aloud all the cards he collected. Repeat one or two more times depending on your students’ enthusiasm. 
6
Production – Combo
At this point have the students do a pair activity. For example if you create a worksheet with a school schedule (a grid that has Monday to Friday along the top, the numbers one to seven or eight depending on your school along the left, and subjects filled in for each day and number) do the following. Teach students this structure:
 A: Do you study subject ordinal number period on day of the week?
 B: Yes, I do! or No, I don’t.
Have two worksheets prepared with different school schedules where only ten or fifteen classes during the week are the same. Ask students to work together (by taking turns using the model dialogue) to determine which ten or fifteen classes they have together. 
7
Review
Do a final class activity at the end of class to recheck comprehension. Ask your students true or false questions about their school schedule. For instance if the class studies English on Mondays and Wednesdays, say “You study English on Tuesday. True or False?” or “You go to school on Sunday. True or False?”
Asking students questions about their schedule using the simple present tense is the most basic way to use days of the week at this early stage. Days of the week will come up time and time again during their English studies. When your students begin studying other tenses questions using days of the week as a time reference is common. “What did you do on Sunday?” or “What will you do on Friday?” type questions will continually review their day of the week vocabulary.