Spelling in English is very irregular, which makes pronunciation very hard to learn. I usually teach pronunciation of vowels by where they are pronounced. Those pronounced with the tongue forward are: /iy/ meet; /I/ mitt; /ey/ mate; /E/ met and /a/ mat. To me, it makes since to teach them this way so they they can differentiate between the confusing sounds, which are close to each other. (beach/bitch is a bitch for them; too/took; cup/cop; and pen/pan).
Today a student asked why the first i in the word "Titanic" sounds like /ay/ and not /I/. It hit me!!! I can now simplify spelling and pronunciation explaining them the way I was taught as a child!
Vowels are usually pronounced either the short or the long sound. We were taught as kids the long and short vowel sounds: A and a, E and e, I and i, O and o, U and u (which can sound like put or putt). The short o, which sounds like AHHH, is confusing for my students because they learned British pronunciation. The letter o is always pronounced long /ow/ as in so or /AH/ as in popular. The only exception I can think of is the word women, in which the vowels both sound like the short i. I once knew a lesbian who spelled women as wymyn, omitting the men, and this is how my students can remember the pronunciation.