Do Shia and Sunnis have a different method of prayers?

Today I went to the masjid at the mall and when I started praying, a shiaa woman came to me and said that I was praying wrong. She was saying that I am not supposed to cross my hand on my belly and she also said that I am supposed to wear abbaya. After that I overheard her talking to her daughter about how sunni people are kuffar Do shiaa people pray differently? Do they think that Sunnis are kuffar?