Just some generalities. Mauser rifles were used all over the world and Mauser derivatives (Springfield, Arisaka) used in others. But the number of countries actually MAKING Mausers is limited. So the "where it was made" is often easier to answer than "where it was used."
The latter answer can usually be found on the receiver ring, where a national crest or symbol and often the name of the nation will be found. Even when the writing is not English or not even in Roman characters, the country will usually be obvious or easily found.
Other means of identifying the manufacturing country lies in proof marks, inspection marks, or military acceptance stamps, either on the metal or the wood stock.
As for other identification, look on the left side rail, where many makers stamped their names. When a full name or identification is not found, other information may be. For example, "Mod. 98" always means the rifle is (or was if it has been modified) a German Karabiner 98k, or K.98k, the standard German rifle of the WWII era.