不要相信那些儿化音规则，我个人是北方人，母语里有儿化音，我感觉完全是约定俗成的，并不是有什么规则，然后根据规则去填加，而有些词就加，有些就不加，加和不加往往是有含义区别的。所有规则，不外乎根据大家的使用来进行总结的，但是，你如果用这些规则任意去自己填加，多半会加错。 你举的例子，没人会说苹果儿。而叫“服务员儿”多少给人不尊重的感觉。而乱用儿化音也会给人一种没受过良好教育的感觉。

Hey Soroush, There are actually 兒話音 dictionaries that you can find. A friend sent one to me once. The general rule is you can add an "er" to something if you want to make it sound "small" and sometimes "cute". So a little lamb can be a 小羊兒, and an ice cream is a 冰棍兒. But really, the best way to learn is to listen to authentic Beijingers speak Mandarin (someone like this https://www.youtube.com/watch?v=GKhD5kHb0gU&list=PLPGK7JARNb4BATIv91PIvDs_iiy3OCOY1). You could even try listening to something like 相聲, which is often performed in Beijng dialect and learn from the pros (try 侯寶林、馬季、郭德綱 https://www.youtube.com/watch?v=Trzwv1QUcAQ） Do make sure you learn from someone authentic though, I've heard many examples of people adding in an "er" when it's not correct to do so. And remember it's seldom used in writing. Laurence

1.一般来说，以a、o、ê、e、u，舌尖前音-i，舌尖后音-i作韵尾，可以儿化。 2.韵尾音素以i、ü为主要元音的韵母可以作儿化处理。 3.韵尾音素为i的韵母作儿化处理时，韵尾i会丢失。 4.韵尾音素为n的韵母作儿化处理时，n音会丢失。 5.以ang为韵尾音素的韵母作儿化处理时，ang鼻音会丢失。

如果不清楚什么时候应该加儿化音，可以选择一概不加。如果在不该使用儿化音的时候使用的话会给人轻佻，滑稽的印象

我来自北京，我平时常说的儿话音包括：串门儿，遛弯儿，小孩儿，有趣儿，宝贝儿。 希望帮到你～～