Modal (auxillary) verbs like 'must' can be a challenge to use in English.

When talking about parenting, someone said, "She must to change her attitude."

I addressed the problem with this sentence on my blog: http://goo.gl/3BJ2ih

Also, I made a PDF guide with more examples and practice sentences: http://goo.gl/8VkrXE

**I am a professional English teacher here on italki.  I would be happy to help you improve your English.  You can view my teacher profile at http://www.italki.com/teacher/493889