I agree Megumi-san. It's impossible to translate it in one way, *for* English preposition has such broad meanings and usages. *For* the examples you gave, Megumi-san's answers are perfect:) Generally speaking, "for" might be translated as ...wo (for something given to me) ばんごはんを　ありがとうございました。Thank you for the dinner. ......te (for doing something) にほんごを　おしえてくれて　ありがとうございます。Thank you for teaching Japanese. .....no tameni (for the benefit of someone) このうたを、はなこさんのために　うたいます。I sing this song for Hanako. .....ni(for someone/something) たばこは　からだに　よくないです。Smoking is not good for your health. .....de (for some price) たった1000えんで　おすしが　たべほうだいです。We can have as-much-as-you-can-eat sushi for only 1000yen. etc. But it really depends on the sentence. It's better to study Japanese sentence patterns rather than translating from English.

It's a little complicated.... (Is anything in Japanese ever easy? lol) It depends on the usage... 晩御飯をありがとうございました。 (bangohan wo arigatou gozaimashita). Thank you for dinner. (I suggest you use an adjective before dinner, such as おいしい (oishii) delicious.) これをあなたに差し上げます。 (kore wo anata ni sashiagemasu.) This is for you. (there are different ways to say this... this one is a kenjougo (humble) expression). I would say "これをXさんに差し上げます。" (kore wo X-san ni sashiagemasu.), though.... It's better to avoid the use of "anata" (it's considered a little rude...) Please let me know if there are different sentences you would like. ^-^ (or more uses of "for"). Feel free to send me a message if you have any questions! ^-^ ~Megumi