我来举例子： 随便扔垃圾是不礼貌的。throw the rubish about is not polite. 在我家不要客气，就当自家一样 。make yourself at home in my home.

礼貌是指对人尊敬。客气是别人对你热情，你要婉拒，而不是把别人对你好看做理所应当问心无愧的接受。

礼貌 can be subject or adjective. As a subject, it refers to manner. As an adjective, it describe someone has good manner. 客气 is usually used as adjective. It describe the way treat other people is very kindly, don't have a strong attitude. There's little bit tricky when you use these word. Since my English is not good enough to express. The answer may not exactly correct. The best way to master these words should come to China or chat with Chinese.