The schwa is the little upside down “e” that you see in a dictionary pronunciation guide. It is pronounced as a short, unaccented UH.
As we know, unaccented syllables are shorter, softer, and lower than accented syllables. Adding this syllable to words makes your speech sound more fluent and natural.
In American English, we use the schwa syllable in many long, multi-syllabic words. How do you know which syllable? You have to listen.
Spelling rules really aren’t much help since the schwa can be represented by the letters A, E, I, O, U. Yes, all of the written vowels can mark a schwa syllable.
The best example that I have is my name, “Jennifer”. Most foreign English speakers pronounce my name “Jen-Ni-Fer”. American English speakers pronounce it “Jen-Uh-Fer”. The “Ni” is replaced by a schwa.
The only way to tell where the schwa goes, other than listening, is to get “old school” and look in the dictionary.