Pronunciation Pet Peeves:
Oh, how silly we must sound to Mexicans when we butcher Spanish!
Yes, they're very tolerant and supportive when we gaff and blunder our way through...and they perhaps understand what we try to say... and, perhaps, we can try a little harder though?
(1) Rather than relying on some silly mnemonic device (like saying "yellow" for "hielo") find out how the word is correctly spelled in Spanish and actually listen to how a native speaker pronounces it.
(2) Learn to correctly pronounce the Spanish vowel sounds. Unlike vowel sounds in English, they are always pronounced the same way, and once mastered with a little effort, will make pronunciation much more accurate.
I realize this is overly simplistic but it has helped me a lot.