English speakers: How do you pronounce a schwa (ə) sound?

In dictionaries, it is represented by the symbol ”ə” in phonetics.

1. Is it one of “a, e, i, o, u”? Do you pronounce one of these vowels for a schwa sound in a word? e.g. the word “given” sounds sometimes like “givin”.
What about “y” as in “martyr”?

2. What is correct pronunciation of “e” in words of past tense (mind->minded) and plurals (price->prices) and possessive (princess->princess’s)? I mean, is it “id” or ”əd” for “e” in “minded”?

3. And if it’s one of the above vowels, which one do you take when they come together, e.g. “motion”?