When I was in college, one of my professors said something about vowels being pronounced differently in Spanish than in English, but I don't remember exactly what it was.
I'm not asking what sounds the vowels make, and the tip I can't remember isn't that the vowel sounds are shorter in Spanish, it was something about how speakers are supposed to hold their lips and/or tongue when pronouncing vowel sounds in Spanish.
English has many vowels (13-16, depending on the dialect) and Spanish has relatively few (just 5). What we consider English vowels are very often diphthongs (i.e. a gliding vowel in the articulation of which there is a continuous transition from one position to another). Take the example: fate /feɪt/; afeitar (to shave).
The two Spanish vowels that this tends to affect are e and o.
The English vowel a is pronounced similarly to the Spanish vowel e, except that in English we say [eɪ], moving the tongue closer to the palate at the end.
The English vowel o is pronounced similarly to the Spanish o, except that in English we say [oʊ], closing the lips at the end.
In Spanish the vowels are pure. They have the same quality (i.e. your tongue/lips should be in the same position) all the way through the pronunciation.
