How you pronounce words in Spanish can matter a lot. Speaking as if you are speaking English can make it difficult to be understood, and putting the stress on the wrong sylable can totally change the meaning of a word. The rules of Spanish pronunciation are consistent, so once you have learned them you can pronounce any word. I am not going to go into too much detail here, but I will throw in a few more pronunciation tips in future posts.
To start with, the stress in a word comes on the last sylable, unless it ends in 'n', 's', or a vowel, when it falls on the second last sylable. Words that do not follow this rule always have an accent over the stressed sylable.
For example -
inglés = English (stress on the 'é')
ingles = groins (stress on the 'i')
esta = this (femenine, stress on the 'e')
está = he/she/it is, you are (stress on the 'á')
So as you can see, putting the stress on the wrong part of a word can drastically change its meaning.