If you learn how to pronounce vowels in Spanish, you can increase your accuracy in pronunciation astronomically!
A is "ah" in Ah-hah!
E is "ay" in pay
I is "ee" in thee (Y is this sound as well)
O is "oh" in Oh no!
U is "oo" in boo
If you're teaching kids this, have them memorize ah, ay, ee, oh, oo and show them flashcards of the written letter as they say its sound. For older children, you can show them how to spell out a word with these sounds. For example, the Spanish word for bank is banco and can be spelt bahn-coh to help the child visually see the sounds for the vowels. As an aided help, clap when you say each syllable.