You use otherwise after stating a situation or fact, in order to say what the result or consequence would be if this situation or fact was not the case.
e.g. Make a note of the questions you want to ask. You will invariably forget some of them otherwise...
e.g. I'm lucky that I'm interested in school work, otherwise I'd go mad.
You use otherwise before stating the general condition or quality of something, when you are also mentioning an exception to this general condition or quality.
e.g. The decorations for the games have lent a splash of colour to an otherwise drab city.
e.g. ...a blue and gold caravan, slightly travel-stained but otherwise in good condition.
You use otherwise to refer in a general way to actions or situations that are very different from, or the opposite to, your main statement.
e.g. Take approximately 60mg up to four times a day, unless advised otherwise by a doctor...
e.g. There is no way anything would ever happen between us, and believe me I've tried to convince myself otherwise...
You use otherwise to indicate that other ways of doing something are possible in addition to the way already mentioned.
e.g. The studio could punish its players by keeping them out of work, and otherwise controlling their lives.
You use or otherwise or and otherwise to mention something that is not the thing just referred to or is the opposite of that thing.
e.g. It was for the police to assess the validity or otherwise of the evidence...
e.g. He didn't want company, talkative or otherwise...