(I post the notes here and mitbbs.)
I listened to American Accent lecture. Here are some tips from the course:
1) "tt" is pronounced as "d". E.g. better, butter
2) Emphasize nouns when you start a conversation. And then emphasize the new information such as the verb in the following sentences:
e.g., Dogs eat bones. They search for bones.
3) The negative part of a sentence should not be emphasized. An exception is "cannot".
So: You can swim. You cannot ski.