儿 would normally go at the end of a charcter couplet but never in the middle, so 哥们儿，爷们儿，姐们儿 but never, 哥儿们，爷儿们，姐儿们。 There are a lot more rules, which depend on the phonetic sound ending of a word, but i dont really know what they are.

"where" can be said 哪里and哪儿，哪里is formal saying，哪儿is spoken language。In the same way, there、here and thing all can be said like that。 Take more exercise when you have nothing to do .没事儿的时候多锻炼。

HAHA, I do it on purpose when i speak to a person from northern China, and they always correct me and told me the right way to use 儿，im not a good learner since i never remember o try to remember how to use it, but it do make up a good conversation, because each time they heard(i put 儿 behind every noun), they laughed and explained .

Compare it to the what?

Simon, john and Ken: Almost all the Chinese people south of Changjiang river and from quite a part north of it do not use the suffix 儿 and the sound i in Pinyin zhi, chi, shi and ri. 儿 is mainly used in the north of China, the area where people pronounce i in zhi, chi, shi and ri is larger than that of 儿, but people living south of Changjiang river and many rigions north of it do not sound it. Instead, they pronounce it as i in Pinyin zi, ci, and si. As regards the pronouncing method of 儿, you may compare it to the