[LouannePiccolo]

I agree with all the above and also want to add that thinking in a language other than your own really only happens naturally...and after a lot of exposure to that language. It can't be forced but asking students to think through what they want to say in English before they say it helps a lot.

I always ask my students to try not to translate in their heads but you can literally see them doing it in the beginning. It stops after a while of constant exposure to English. And although, I don't think that it is realistic to say that teachers should only ever speak in English in their classes, it does help if students hear lots of English and very little of their mother tongue during class.

I sometimes ask students to actively "think" in English during one whole hour every day if they can handle it. This means literally talking to themselves in their own heads for an hour a day. It's easy in the car, while you're brushing your teeth, waiting for the bus, exercising etc.. Some like this exercise and some don't. Don't force it, it'll come on its own.