Theory:

Pronunciation 6 - The Dominant syllable

Every word in English has one and only one dominant syllable.
For example, each syllable in the word banana is not pronounced the same.
The second syllable, NA is dominant, and so its sound is longer and stronger, while the other syllables have a sound that is shorter and weaker.
The correct pronunciation of the word Banana is ba NA na.

It was mentioned earlier that SCHWA was the most important sound in English.
The reason is that in most cases, the syllables of a word which are not dominant have the SCHWA sound, like LE in tabLE, or ER in paintER.

Each dominant syllable has a vowel sound in the middle, and that vowel needs to be pronounced correctly for the word to be easily understood.
For example:
The word Fire has 2 syllables, FI and RE.
The first syllable FI is dominant, so the word is pronounced FI re.
Because the second syllable is not dominant, it has the SCHWA sound.
The dominant syllable has the double vowel sound AI as in EYE in the middle.
So FIRE is correctly pronounced F EYE SCHWA.

If, by mistake, a different vowel sound is used, for example the short I as in sIt, the word FIRE would sound like Fi SCHWA, and nobody would understand it.
The key to being understood is using the right sound in the right place.

It is common in English for one word to have two different meanings, or for the same word to be a noun and a verb.
The only way to identify the different meanings is by the positioning of the dominant syllable.
For example:
The noun PRESENT is pronounced PRE sent (schwa) and the verb PRESENT is pronounced pri ZENT.

Some exercises of these kinds of words are given below: