5. Be aware of intonation and sentence stress.
Not all words in a sentence have equal stress, and generally only the "information" words (nouns and verbs) are stressed.
'Where's the 'pen I 'gave you?
'Where's the 'red 'pen I 'gave you?
Changing stress
Sentence stress isn't "fixed" like word stress. In fact, you can stress words that are normally unstressed in order to highlight different meanings.
For example : I 'love you. (Love, rather than just like.)
'I love you. (With the stress on I to highlight that it's me rather than another person who loves you.)
I love 'you. (And nobody else.)