Research has confirmed that adults can be better language learners than kids.
Studies have found that under the right circumstances, adults show an intuition for unexplained grammar rules better than their younger counterparts.

Adults can learn languages

Rote repetition isn’t enough.
Coming up with mnemonics about your target word helps glue the word to your memory way more effectively. Basically, you tell yourself a funny, silly, or otherwise memorable story to associate with a particular word.

Using mnemonics when learning a new language

<ul>
<li>Accent. Time with a native, a good Youtube video explaining the sounds, and practice for a few hours may be all that you need!</li>
<li>Intonation. The pitch, rise, fall, and stress of your words. When you repeat sentences, you have to mimic the musicality of them.</li>
<li>Work on your social and cultural integration. Observe people directly, or watch videos of natives you’d like to emulate from a target country. Really try to analyze everything that someone of your age and gender is doing, and see if you can mimic it next time you are speaking.</li>
</ul>

Sounding more native in a new language

Focus on one language at a time until you reach at least the intermediate level. Take each language one by one, until you reach a stage where you know you can confidently use it. And then you may just be ready for the next ones!

Become a polyglot

<ul>
<li>A completely free course that keeps getting better is DuoLingo.</li>
<li>The Foreign Service Institutes</li>
<li>The Omniglot Intro to languages</li>
<li>BBC languages</li>
<li>About’s language specific posts</li>
<li>The huge database on Forvo</li>
<li>Rhinospike</li>
<li>Google Translate.</li>
</ul>

The best resources for a foreign language are free

To start developing your SMART goal (Specific, Measurable, Attainable, Relevant, and Time-bound) in a language, become familiar with the European Common Framework that defines language levels. 
<ul>
<li>Know how well you want to know the language.</li>
<li>To make your project Time-bound, a short end-point of a few months is recommended.</li>
<li>Make sure to track your progress and use an app to track completing daily essential tasks.</li>
</ul>

Create SMART learning goals

You can’t ever truly “learn” a language, you get used to it. It’s not a thing that you know or don’t know; it’s a means of communication between human beings. Languages should not be acquired by rote alone—they need to be used.
One of the best things you can do in the initial stages is not to try to get everything perfect, but to embrace making mistakes.

Learning languages: embrace mistakes

In English, just 300 words make up 65% of all written material. We use those words a lot, and that’s the case in every other language as well.
Use flash cards of the most frequently used words (or words themed for a subject you are more likely to talk about)

Learning a new language: knowing the most used words

<ul>
<li>To hear the language consistently spoken, you can check out TuneIn.com for a vast selection of live-streamed radio from your country of choice. </li>
<li>To watch the language consistently, see what’s trending on Youtube in that country right now. </li>
<li>To read the language consistently, you can find cool blogs and other popular sites on Alexa’s ranking of top sites per country.</li>
</ul>

Interact in your new language daily

Cognates are “true friends” of words you recognize from your native language that mean the same thing in another language.
For instance:
<ul>
<li>Words like Action, nation, precipitation, solution, frustration, and thousands of other -tion words are spelled exactly the same in French, and you can quickly get used to the different pronunciation. Change that -tion to a -ción and you have the same words in Spanish. Italian is -zione and Portuguese is -ção.</li>
<li>Many languages also have words that share a common (Greek/Latin or other) root.</li>
<li>Even languages as different as Japanese can have heaps of very familiar vocabulary.</li>
</ul>

Learning cognates

You must speak the language right away if your goals in the target language involve speaking it.
<ul>
<li>Learn some basic vocabulary. </li>
<li>Do this for a few hours, and then set up an exchange with a native speaker—someone who has spoken that language their whole life. </li>
<li>You only have to learn a little for your first conversation, but if you use it immediately, you’ll see what’s missing and can add on from there. </li>
<li>You can’t study in isolation until you are vaguely “ready” for interaction.</li>
</ul>
You can get private lessons from one-on-one Skype-based lessons.

Learning a new language: Skype for daily spoken practice

<ul><li>From the start, speak at least an hour a day in the language. Have varied conversations.</li><li>Ensure that your conversation is improving—not just “general language skills” through some vague list of words.</li><li>Lots of practice and study to improve those spoken sessions tends to get you to lower intermediate level.</li><li>This is the point to return to academic material and grammar books, to tidy up what you have.</li><li>To get into the mastery, start reading newspapers, technical blog posts, or other articles that won’t exactly be “light reading.”</li></ul>

Conversational to Mastery 

I've written about how I learned to speak, read, and write Japanese, Mandarin, and Spanish. I've also covered my experiments with German, Indonesian, Arabic, Norwegian, Turkish, and perhaps a dozen others. There are only few language learners who dazzle me, and Benny Lewis is one of them.