The commonly preferred language is Spanish. The demand for Asian and Russian languages is also steadily growing. If you know a second language, mention it in your resume and specifically mention about the level of your fluency in that language. You must also be prepared to demonstrate your language skills in the interview. Whether the job description speaks about the language as a requirement or not, do underscore your language skills.
It is not possible to connect your language skills to higher pay; but it is evident that your prospects of getting a job are more if you speak two or more languages. Many global companies specially look for people who have experience of working with people from cultures they serve. The fact that you have served abroad for sometime is enough to have an edge over others in the job market.
You may face some difficulties in learning a language now. But don't get disheartened. Of course, it is a known fact that one can learn a language easily in his or her childhood. But linguists say that is true regarding pronunciation. Adults have an advantage as far as grammar and syntax are concerned. They become proficient in that new language and their level of proficiency may even get jobs that require very high command over such languages.
Nowadays, learning a new language has become affordable. You can even get trained in any language free, thanks to online facilities. There are many Web sites that offer free online language instruction.
Besides getting organized instruction, it is better to get hold of a magazine or a newspaper in the language you are learning. You will also be benefited if you watch movies and listen to radio stations in your target language. Visit places where the language is exclusively spoken. For that you needn't necessarily take up an expensive travel. Just go to your city's little Italian neighborhood, if you are learning Italian, or regularly visit a Chinese restaurant if you are trying to speak Chinese. Or for that matter make friends with a family that speaks in your target language. It is very important to watch how a native speaker shapes his mouth when talking and imitate him. Find a friend who speaks your second language. Get hold of a phrase book and consult it frequently. These are some steps that can take you to your destination.
Learning a new language is like learning music. You have to regularly and daily practice and pamper your newfound love. You will be surprised to see the results.