How Japanese say ”thank you”.

1 Arigatou( ありがとう)

1-1 Arigatougozaimasu (ありがとうございます)

1-2 Makotoni-Arigatougozaimasu(まことにありがとうございます)

Extra edition 2 Doumo(どうも)

/1  Arigatou(ありがとう)

  This is applicable anytime except for business and the person you have to respect.

1-1 Arigatougozaimasu(ありがとうございます)

   Arigatougozaimasu is more official way.

1-2 Makotoni Arigatougozaimasu(まことにありがとうございます)

  This one’s mainly used for e-mail or when you are faced in someone who has great authority.

2 Doumo (どうも)

This is abbreviation of “Doumo Arigatou (どうもありがとう)”.

When you were helped by someone who are close to you like friends or whatever, you can use this words in a casual way. This words will make you more Japaneseish.