One of my leads sent me an e-mail saying he was having trouble distinguishing the languages.  I understand that frustration only too well.  So I threw together this little "language primer" to help folks distinguish between languages, specifically for Stone Rains, but also in general.  It's not great, but it might prove helpful for most cards...

European Languages:

In general the easiest way to tell these languages apart is by looking at the copyright line. In English this line includes "All Rights Reserved." In other languages it contains different text. Unfortunately between 5E and 6E wizards stopped printing all-rights-reserved on their cards, so after 5E you'll have to differentiate languages in other ways.

ENGLISH:

Stone Rain. You know how to recognize this! Includes "Destroy target land." in the textbox.
 

FRENCH:

Pluie de pierres.
The earliest printings of Stone Rain in French (BB and WB revised) have the card text "Le terrain cible est detruit." (Target land is destroyed.) Ever since then it has been "Destruisez le terrain cible." (Destroy target land.) The only exception being Portal and Portal 2 where it was "Destruisez un terrain de votre choix." (Destroy one land of your choice.) Beyond that, to recognize French cards requires a passing knowledge of French. Looking for "le" and "la" is insufficient, other European languages use those as well. French, Spanish, and Portuguese use "de" for "of". As in Spanish, quotation marks in French look like little angle brackets (i.e. << and >>). Earlier French cards have "Tous droits reserves" in the copyright line.
 

GERMAN:

Steinhagel (in BB RV it was Steinschlag, but has been Steinhagel ever since).
Recent Stone Rains have "Zerstore ein Land deiner Wahl." in their textbox. In 4E it was "Zerstort ein Zielland.", in WB RV it was "Zerstort ein Gelande", and in BB RV it was "Vernichtet ein bebliebiges Land." German is generally the easiest language to recognize after English. Nothing else looks like it. The article "ein" is very common (it serves the same function as the word "a" in English "Ein Hunt" = "A Dog".) The other common German article "das" is basically equivalent to "the" in English. Earlier German cards have "Alle Recht vorbehalten." in the copyright line.
 

ITALIAN:

Pioggia di Pietre.
Most of these say "Distruggi una terra bersaglio." in their text box. BB and WB RV have "Distrugge una terra scelta." Italian has lots of double letters and many words that end in "i", or other vowels. Italian uses "di" for "of". Quotation marks in Italian and Portuguese resemble those used in English. Earlier Italian cards have "Tutti i diritti riservati" in the copyright line.
 

PORTUGUESE:

Chuva de Pedra (in some sets it was Chuva de Pedras, namely 5E, Ice Age, and Mirage).
All Portuguese Stone Rains have "Destroi o terreno alvo." in their textbox, sometimes with a hyphen between "terreno" and "alvo". As far as I know Portuguese is the only language that uses the article "o" to mean "the" or "a". Quotation marks in Italian and Portuguese resemble those used in English. Earlier Portuguese cards have "Todos os direitos reservados" in the copyright line.
 

RUSSIAN:

9E will be black bordered and include Cyrillic symbols. I haven't seen a language sample for Russian yet. Only Ravnica and 9th Edition are printed in Russian so far.
 

SPANISH:

Lluvia de piedras.
Most of these say "Destruye la tierra objetivo." As far as I know, Spanish is the only language that uses "y" as the conjunction "and". French uses "et", Portuguese and Italian use "e", and German uses "und". As in French, quotation marks in Spanish look like little angle brackets (i.e. << and >>). Earlier Spanish cards have "Todos los derechos reservados." in the copyright line.

Asian Languages:

MTG cards can be found in Japanese, Korean, and two varieties of Chinese (Simplified and Traditional). The quickest way to differentiate between them is to look at the character that appears at the end of sentences. This character is easy to find on Stone Rain since Stone Rain only has the equivalent of "Destroy target land." above the flavor text. Korean uses a dot, the other Asian languages use a hollow circle. In Japanese, the hollow circle appears aligned with the bottom of the text, just like a period. In Chinese the hollow circle sentence-ender is *sometimes* centered vertically on the line (it appears next to the MIDDLE of the previous letter, instead of at the bottom), however in the latest S-Chinese sets Wizards has started aligning this circle with the bottom of the line.

KOREAN:

Uses a dot to end sentences, and this dot looks just like a period, it appears at the end of the sentence, lined up with the bottoms of the letters. Also Korean letters are very angular, including lots of square shapes and vertical strokes, with occasional ovals. You wont see many slanted strokes in Korean. Also, Wizards has stopped printing in this language, the last set printed in Korean was Urza's Saga, so if you are looking at a 9th edition asian card, it ain't Korean. The easiest Korean character to recognize on Stone Rain is probably the fifth one from the left shown in this sample. It looks like a fraction ("2 over 2").
 

JAPANESE:

Uses a circle to end sentences, and this circle appears lined up with the bottoms of the letters. Japanese letters tend to be a lot rounder than Korean letters and there are common symbols that appear on practically every Japanese card. The Japanese symbol for the word "of" (as in "Rain _of_ Stones") looks like a lowercase g or a 9 lying on its left side. In the language sample shown here it is the 3rd character from the left, it also appears in the card title. If you see this symbol on a card, it is Japanese. Also, with regard to Stone Rain in particular, the character right before the "period" at the end of the sentence looks like a stylized swirly number 3. You won't see this on non-Japanese Stone Rains.
 

TRADITIONAL CHINESE:

Wizards has stopped printing in this language, the last set printed in T-Chinese was Mirrodin. All T-Chinese cards use a circle as a sentence-ender, and the circle is centered vertically as shown in the language sample here. Traditional Chinese characters tend to be very complex, and are mostly angular with rounded corners. Also, when Wizards printed T-Chinese, the characters are not printed with "strokes". (The letters do not appear caligraphic, all the lines are of uniform thickness, instead of going from fat to thin like a brush stroke.) The character I find easiest to recognize on T-Chinese stonies is the 3rd from the left in the language sample here. It looks like a simple rounded rectangle divided into 3 equal sized sections... like a little ladder or a stack of boxes. This character *does* appear on S-Chinese cards as well, but it looks very different.
 

SIMPLIFIED CHINESE:

Wizards is still printing in S-Chinese. All S-Chinese cards use a circle as a sentence ender, and in the older ones this circle is centered vertically (as shown here). Unfortunately, somewhere between 7th Ed and 8th Ed wizards dropped the circle to the bottom of the line, just like in Japanese. Fortunately it is easy to tell S-Chinese from Japanese because it doesn't have the Japanese "of" symbol, or the "swirly 3". To differentiate S-Chinese from T-Chinese look at the style of the letters. S-Chinese letters look like they were painted using a caligraphic brush. In other words, they have "stokes" the lines change thickness, going from thin to fat or vice versa. S-Chinese has the same "ladder" symbol that T-Chinese has, in the third position on Stone Rain's text box, but if you compare the two ladders you'll see that the S-Chinese one look more curvy and stylized, whereas the traditional one is more plain. The stylized brush strokes make Simplified Chinese look more fancy and old fashioned than Traditional. Ironic, eh? The running joke is that S-Chinese looks traditional, and T-Chinese looks modern.