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