Most personal trainers are basically told what to do by lawyers who don't understand how the body operates. Take what they say with a grain of salt, and do your own research. There are plenty of good reference sites online, but message boards, even this one, are not always the best place to learn, because you never know who or where the information comes from.
My advice, pick a goal, find an accredited specialist or coach who has written books/articles relating to your goal, and start there.
If you're looking for lifting info, start with Mark Rippetoe's "Starting Strength."
“…what a disgrace it would be for a man to grow old without ever seeing the beauty and strength of which his body is capable.” - Socrates