Particle が and は
This time, I would like to explain what the difference is between particles が and は. When I talked with my language exchange partners and correcting some friends'postings, I realized that understanding their differences are s common difficulty for beginners of Japanese learners.
The point is what you would like to emphasize in your sentences.
Let imagine, your name is John Smith. You are in a hospital and waiting your turn. Then, finally a nurse calls your surname 'Mr. Smith!' But you are not sure she called you or not. Maybe, there are other Mr. Smith because some other people are also looking around. Then, the nurse shouted your full name, 'Is there Mr. John Smith?'
So, now you are sure she called you, not a person who is sitting next to you or a person who sitting in front of you and reading a book. Thus, you go close to the nurse and say 'I am John Smith.' In this case, you emphasize 'I' and imply 'I' am John Smith who you are looking for, not the person who is sitting next to me, nor the person who is sitting in frot of me. So in this situation, the sentence, I am John Smith, has to be translated 私'が' ジョン スミス です。When you use 'が', the sentence must emphasize 'subject', not 'objects'.
Well, how about 'は'?
So, now you are still John Smith and in the hospital. Suddenly, a stranger came toward you and asked, 'Are you, by any chance,Mr. John Brown?' Unfortunately, you are John but not Brown. So you may answer 'I am John Smith, not John Brown.' In the sentence, you emphasize your name, John Smith which is the object. So in Japanese, you can say '私はジョン スミス(じょん すみす)で、ジョン ブラウン(じょん ぶらうん)ではありません。' So, as you can see, when you would like to emphasize an object, not a subject.
So I hope now you can easily translate the sentence, He is my favorite actor, in Japanese.
There are two versions.
1)かれ は 私の 好きな 俳優(はいゆう)です, in the sentence emphasizes 'actor'.
2)かれ が 私の 好きな 俳優です, in this case, the sentence emphasizes the subject, わたし.
I would like to cut the explanation about them because I am fed up with typing with a phone.
If you have any question about these particle, you just ask your language exchange partners. And unfortunately if it is me for you, just ask via Skype. I'm willing to answer your question.