Now, you may look back at the sentence we were working on, and wonder how we figured out what the rhythm was in the first place. The answer, of course, is that we didn’t figure it out; we just “felt it out.” We said the sentence as it came to us naturally, and noted which syllables we stressed and which we didn’t.
However, there are rules that we use in English, without even realizing it, to choose when to stress which syllables. As best I can figure them out, they go as follows.
Each multi-syllable word has its own intrinsic stress pattern, and you can tell what the pattern is just by saying the word. Do not change this pattern unless (a) the word ends with two unstressed syllables, and (b) the next word starts with an unstressed syllable. If that happens, then you can change the last syllable of the first word to be stressed.
Single-syllable words (e.g., “dog,” “cat,” “chair”) can be either stressed (long) or unstressed (short), depending on what you need to make the other rules work.
If the first syllable of the sentence is a single-syllable word, it must be stressed unless it is a possessive pronoun (like “my,” or “your”), a preposition (like “to,” “for,” “or,” “on,” etc.), or an article (like “an” or “the”). In those cases, you probably shouldn’t stress it.
Try to alternate long and short syllables. So, if a single-syllable word comes right before a multi-syllable word, the single-syllable word should have the opposite length to the first syllable of the multi-syllable word. (For example, the “and” in, “And afterwards,” should be short, not long.)
There are two important exceptions to Rule #4. First, adjectives or adverbs that precede nouns are always long. (For example, “green caribou” is “green caribou.” Likewise, “fast tiger” is “fast tiger”) Second, an article (i.e., “the,” “a,” and “an”) or possessive pronoun (“my,” “your,” etc.) should always be short, no matter what comes after it.
If a stressed syllable is followed by multiple unstressed syllables, they all have a tendency to sound like they belong to the same word. If all the syllables do not belong to the same word, therefore, it is often good—if possible—to change one of the unstressed syllables so that it becomes stressed.
To contrast what you are saying with an alternative, you may stress an otherwise unstressed syllable. For example, the word “the” in, “Are we going to the Walmart?” should be unstressed. But, if you wanted to emphasize that you were going to the Walmart, rather than simply a Walmart, you could stress it.