Use these techniques on texts of your own and in conversation.
(1). Take some written material and mark the intonation, then the word groups, and finally the liaisons.
(2). Practice saying it out loud.
(3). Record yourself and listen back.
In conversation, think which word you want to make stand out, and change your pitch on that word. Then , run the in –between words together in the valleys. Listen carefully to how Americans do it and copy the sound.