Yes, you must use the German verb patterns. You can't infer the German patterns from he English patterns. etwas (Nom) gefällt jemandem (Dat) jemand (Nom) mag etwas (Akk) You can look up the patterns in a good dictionary, e.g. Pons: http://de.pons.com/%C3%BCbersetzung?q=gefallen&l=deen&in=&lf= (the first entry is the participle of "fallen", the second entry is the one) Also, it helps to learn some German grammar by reading about the rules explitely. AFAIK Rosetta stone doesn't do this. See e.g. http://www.mein-deutschbuch.de/lernen.php?menu_id=16

You found it yourself. "Es gefällt mir" has as the grammatical subject the thing or person that is being liked. So "I like this shirt" becomes "Dieses Hemd gefällt mir". And what is the subject in the English sentence becomes an indirect object, hence the pronouns "mir, dir, ihm, ihr, uns, euch, ihnen/Ihnen". As "Ich mag dieses Hemd" means almost the same, you can stick to that - for the time being - it behaves in exactly the same manner as its English counterpart.

You can think of it as "It is a good concert to him". Although my english is not that good to say if thats absolutly correct. But at least its a good example to explain that. As you see its "to him" which you can see as an analogy to the german Dativ-case. Many german expression are translated like that. for expample "She said it to him" "Sie hat es ihm gesagt". Also know that there is often an object in the sentence when the Dativ-case appears. In english you only know Objects of the personal pronouns as I know. In german there is this case for all nouns. The only difference of this sentence pattern is, that in "Ihm gefällt das Konzert" ,"Das Konzert" is the object in my translation it would be the subject.