Pinyin offers lots of help in knowing how to pronounce characters - but you need to be sure you know how to pronounce the pinyin - and that isn't always obvious.

This resource gives you a check list with sound files for you to refer back to:

http://www.ctcfl.ox.ac.uk/Pinyin_Notes.htm

(Of course, one of the main advantages of pinyin is that it gives you the tone mark - so never write pinyin without adding tone marks or you lose one of the biggest advantages)