ă is a shorter a sound
â is a shorter ơ sound
ê is more like "ey" rather than "eh"
I and y are both "ee" sounds
ô is like "oh" but your mouth is rounder
ư is like saying "ooh" but with your mouth stretched wider
However, keep in mind that:
ia is written as iê when there's another consonant sound after it (kia vs kiên) and the same is true for ua/uô and ưa/ươ.