One of your parents or legal guardian has to fill out form AN for you, assemble the required evidence (guide AN) and pay the fee. You also need to obtain two references for a section of form AN, one from any person with professional standing (minister of religion, doctor, teacher, etc.) and another one from a person with professional standing who is also a british citizen (obv. they may both be). You also have to provide evidence of knowledge of life in the UK, by taking a Life in the UK test (as I guess your level of English is above Entry 3 ESOL so you are not eligible for the citizienship courses). UKBA say they try to make a decision within 6 months, however they may take longer.
You can download form AN, the booklet and the guide (really read this, it's the most clear and reliable information you can get!) from http://www.ukba.homeoffice.gov.uk/br...aturalisation/. For the Life in the UK test have a look at http://lifeintheuktest.ukba.homeoffice.gov.uk/.
Upon acquisition of a foreign nationality you automatically lose your German citizenship as per German law. However, you can apply for an exception (which is always granted afaik) by requesting to retain German citizenships because of existing strong ties with the country (such as your already mentioned German family ties). I think you may best look at the BMI website (http://bmi.bund.de) for information on that. However, it is important that you get this exception before you are naturalised so best check this at the same time as the naturalisation process.
Last edited by MagLatus; 12-05-2012 at 17:36.