Original post by moggingtonGerman isn't offered at my school, but I'm pretty sure that the layout of the course itself must be pretty similar to other languages like French. A Level languages are tough, but if you're prepared to take on the challenge, it's genuinely one of the most useful skills to have. The way in which languages are learnt at A Level is very to different to GCSE, you get the opportunity to explore language in much greater depth, with an opportunity to read the literature of the language in question too. A friend of mine is doing it at AS and gets some of the strangest essay questions - one was something along the lines of 'to what extent is being single the best way to be?'
I'd argue French would perhaps turn out to be more useful later on in life, as its more widely spoken, but if you prefer German (or would want to live in a German-speaking country), the decision is up to you.
Geography's a brilliant subject at A Level. If you've studied it at GCSE, much of what you learn at AS is merely a continuation of that and the difficulty level doesn't rise significantly in the transition (in comparison to other subjects, at least). The one aspect where it does get tougher is that it is an essay-based subject, and the transition from answering a maximum of 6 mark questions to having to write entire essays on topics can be tricky to master. However, practice makes perfect, and you'll soon discover that essays for Geography are not particularly long ones, usually ranging between 1-1 1/2 sides of A4. It goes superbly with History if you're studying Modern History and have an interest in Politics, but also very well with Maths as the fieldwork sometimes requires statistical skills. Fieldwork is a really key point as to why Geography is a valuable subject - it provides you with skills in research, data collection etc. which very few other subjects offer.
All three are very useful A Levels to have, good luck with making your decision!