This website was created to help people improve theirAmerican English pronunciation. At the core is a series of videosexplaining in detail how each sound is created, as well as a blog.
@M-whenever you run into problems with the vowel charts, that are in your book (regarding, not being sure if you are making the correct sounds) then try to find and use an example like what are to be found on this link. Teach yourself the basics relative to the pronunciation brackets that are in the dictionary.