Used well, your students first language has a valid place in your EFL classroom. Here are some ideas of activities to incorporate L1 into your lessons:
1) Translation Consequences
Take a piece of paper for each student and give them a phrase in English, using recent language acquisitions, or ask them to write their own.
Next get them to translate these phrases into their L1 (make sure this will be the same for at least pairs or groups if not the whole class) and fold the paper to hide the original phrase.
The students then hand their paper to their neighbour who translates this L1 phrase back into English.
You can either continue this until the page is full or stop here, open the paper and have the students discuss any differences.
2) Interpreter Game
Their are many variations for this activity, and as interpreting for family and friends while on trips or when they come across English is actually something my students regularly do, they find this activity useful, and fun.
Put the students into groups of three and give them a situation, for example in a restaurant, bank, hotel. One student speaks only L1 and the “interpreter” must interpret for the English speaking waiter/receptionist etc.
Alternatively try this whole-class activity- one student chooses which superstar he will be (or you can choose someone who you studied recently or who is in the news). The rest of the class are journalists and they are interviewing the star at a press conference, you can choose whether the star or the journalists speak L1 and, as before the interpreter has to translate the questions and the answers.
My students love watching films in class, however I am always keen to ensure these lessons remain learning experiences and don’t fade into time out with no apparent objective. One of the activities we do is watch a small moment of film in English (with English subtitles if necessary), get the students to write their own subtitles in L1, then watch it again with L1 subtitles and compare them to those the students wrote. It’s interesting to compare the two forms of subtitles as well as the difference between the spoken dialogue and written forms.
4) Comprehension Check
As well as simply checking orally that students have understood a written or oral text, I give summaries in L1 with some intentional errors, and ask them to correct them. Alternatively give two or three versions and have the students choose the correct one.
5) Grammar Translation
Shock, horror! Dare I actually suggest this method to fellow teachers in this day and age?!! Well, yes actually. Recently I was explaining to a year 7 class (first year of L2 for many of them) that in English we use BE to talk about age, as in French they use HAVE it was logical to mention this. As many of my students speak other languages, this developed into an interesting discussion about how to talk about age in Russian (neither BE or HAVE apparantly), Finnish and Khazak. I’m not suggesting using it all the time, but as in this case I wanted to draw attention to the difference between English and French it was a useful exercise.
6) Learning Skills
Teaching in a secondary school, I spend a lot of time, especially at the beginning of the year, talking to students about how to learn. It seems this (in my eyes essential) part of the school curriculum is missing in other classes, and I give them useful tips on how to go about learning vocab and revising for tests, in all their classes, not just English. These discussions are usually in L1, especially for lower level classes, although they are repeated regularly, and sometimes in English, during the school year.
There is a valid place for L1 in the EFL classroom, and by defining and thinking a little more deeply about this place I actually find students are more willing to communicate in English at other moments.