If you pay attention to mastering the basics of the Spanish language your ability to speak Spanish like a native speaker will dramatically increase. Infants can sound more native because they pay close attention to detail. Not because they posses magical abilities to learn languages better.
Know your ABC’s
The first thing you must master is the vowels of the alphabet. Most people overlook this and consistently pronounce words incorrectly. Spanish is a phonetic language so words sound exactly how they are spelled. In English vowels have several sounds, but in Spanish there is a single sound for every vowel and you have to stick to that sound no matter how many times that vowel appears in a word.
Take the word colombiano for example. A common mistake is to pronounce the words as columbiano. You should maintain the same sound for the vowel o. The word should be pronounced coh-lohm-bee-ah-noh.
Another example is the word típico. Many times people pronounce this word as tih-pee-coh. The letter i should sound the same throughout the word. The word should be pronounced tee-pee-coh.
For more practice you should look up Spanish words that have the same vowel repeated more than once and practice saying those words so you will train your brain to remember this pattern. Within minutes you should notice your “native” accent starting to develop.
Think about the letters T and D
As native English speaker we may not realize that we have to ways of saying the letter T. There is one when we say the word think, and another when we say the word ticket.
We want to “think” we using the letter T in Spanish. When pronouncing the word trabajo its better to say thrah-BAH-joh than trah-BAH-joh.
We also want to “think” when we pronounce the letter D. Forget about saying the letter d like its English counterpart. The letter D in Spanish makes a “th” sound. When you say the word poder it should be pronounced poh-there and not po-dare.
If you read this and do not practice it you will fall back into your old habits of pronunciation. You should go across the internet to sites like BBC Mundo, Rtve.es, or any other spanish language sources to practice saying the spanish vowels with the same sound. Find a friend to speak with and have fun while learning the language.
Cuidate y hable mejor!