The main difference in the pronunciation is the speed, the Portuguese is a little slower, something that is clearly visible in Spanish pull the very sound of the "r" which does not happen in Portuguese.
One more tip, the sounds of the Portuguese sound is more nasal, for example the sound of the letter "b" in Spanish you know, but in Portuguese, has a sound more closed.
Tip, try to hear the sound of letters, learning this, you already know pronounce the words, it is not equal to English, that a letter has several sons...
See you!
Sorry for my english.