How do I make students speak English in class instead of using their mother tongue in communication ?

Don't speak their language.Just speak english and finally ,they will discover that they will have to follow you.also , give simple instructions in English if they are young.

"Practice what you preach" If you want them to follow what you teach, you should lead by example. If this does not seem to work you can implement a light consequence if someone is caught speaking in the mother tongue, like maybe letting them dance or sing in front of the class, this will enable them to speak English and avoid speaking in the native and at the same time they will have fun catching the one who speaks in the vernacular.

Learning language like learn how to drive a car, I mean you have do a low with them that the student who speak his mother tounge language has to bring a choclate or sweets next days, also, they may make alot of mistake at the begining but at the end they well learn, so we we learn how to drive will do many accident but at the end we will be a good drivers, this my way in teaching,

Regards

The answer varies according to the age group. In the case of teenagers (and if the class is homogeneous) the teacher has to be very diplomatic and strategic. There will be many attempts to use L1 in the classroom and no matter what you do, they will not yield. So I suggest a negotiation with the kids. There could be 2 –3 golden rules that rationalize L1 use in the classroom:

1.       Negotiating: meaning – I don’t understand. / Who is going to do what in the group? Letting students organize themselves in the group work.

2.       Clarifying (especially directions) – Say it in English, somebody will say it in L1

3.       Using a T-chart to monitor students' language use – Put a tick in the box each time you use L1 or English.

                                                     English spoken      vs               L1 spoken

 For self-monitoring purposes, students can review the chart every two days or so, then a discussion follows.

There must be some non-negotiable instances, though, i.e. when students are practicing a certain grammar rule, idiom, expression, etc. they have to use English exclusively.