Obviously, this is not the start of my project, given that it is June, it is hot and sticky and we are almost at the end of a year. I just wanted to mention a few things before I got the ball rolling. The aim of teaching a foreign language is ultimately to get your learners to communicate in it. Therefore, it makes sense to lead by example, doesn't it? I find it a little weird teaching in language sandwiches - English, German, English; like it isn't real. Your learners need to see that it is a real tool for really using in real situations. Your classroom is a mini Germany, France, Spain etc. Everything that happens inside it should be, for the most part, conducted in the language of the lesson. Teachers that enter should be trained to speak only in that language when they enter, or at least try! Learners love to see other adults having to abide by the same rules they do and are very impressed when Mr Blahblah shows them he can 'get by' in German etc.
There are of course things you can do to help this communication happen. Your walls and noticeboards are a brilliant place to display useful language, or if you are short of space, why not provide 'language mats' to give your learners the vocab they might need to say various important things, such as 'Can I go to the toilet?'
They will not need all of the language on there to begin with, but they can start to make connections and maybe surprise you by coming out with something else from the mat that they have worked out themselves! Do not underestimate the power of teampoints and prizes, or indeed, praise. Learners like to win, so use that to your advantage.
The main thing is that you start off small and build up, so routines such as taking the register, handing books out and keeping score become a language opportunity. Then you can build it up to asking for points and giving reasons why they should have those points etc. Before you know it you have got complex 3 or 4 clause sentences, just as a result of the 'incidental' language.
You have to put to one side your thoughts about not having time to fit in the content language and understand that THIS IS the content language that they need. The structures and phrases you teach them to communicate with in lessons are the structures and phrases that they can use for a variety of 'topics' if you are clever about it and choose wisely.
Finally, what if they don't understand you and switch off? This won't happen if you use cognates and simple language to begin with. There is always a way to make yourself understood, including gestures and mimes; anyway, isn't this what we do when we travel to other places - we make ourselves understood! Your learners will feel great when they make themselves understood in your lesson too!