The usual pattern at the end of declarative and imperative sentences (but not questions) is that
- the vowel of the last syllable with primary stress has a somewhat raised pitch, and
- the pitch must fall away from that point to a low pitch.
If the last stressed syllable is also the last syllable of the sentence, then the fall in pitch is achieved by a "glide"—the pitch falls continuously while the vowel is being pronounced.
But if the last stressed syllable is followed by one or more unstressed or less-stressed syllables, then the vowel of the last stressed syllable is spoken with a high pitch throughout, and the pitch drops—"steps down"—on the following syllables.
In most cases, therefore, you need only look at the last stressed word. If it has only one syllable, or its primary stress is on its last syllable, you speak the final syllable with a glide. If its primary stress is not on its last syllable, you speak the last syllable with a high pitch and step the pitch down for the syllables which follow it.
In the examples below the stressed syllable is written in CAPS; the pronunciation is indicated with ↘ for a glide and ↴_ for a step.
John's giving a TALK↘.
John's giving a LEC↴_ture.
John's giving an IN↴_terview. Note that the primary stress in the word interview falls on the first syllable. In this case there will actually be a small rise in pitch and glide down on -view, *but this is far less marked; the 'information' about the sentence coming to an end falls on the IN–ter- stepdown.
She is friendly and outGO↴_ing.
He is quiet and SHY↘.
Sometimes, however, the last word does not bear the final primary stress; the stress may move to an earlier word to signify a contrast. In this case, you step down from the stressed syllable. For instance.
I don't hate him, I hate YOU↘ has the ordinary stress, but
I don't love you, I HATE↴_you has the stress moved back.
And some words have different stresses with different meanings. Outgoing, for instance, has a primary stress on -GO- when it means "extroverted", but on OUT- when it means departing:
Marcia is the incoming president and John the OUT↴_going. Again, this will have a secondary glide on -ing, just like -view in my third example.