Perhaps the best possible way would be to immerse yourself into the language environment. Fortunately, the 21st century offers countless possibilities to delve deeper into the language of almost any country. If you already have some basic knowledge of the language of your choice, look for cartoons and other entertaining materials meant for children--the vocabulary and grammar in these materials is usually rather simple, so you will not have significant problems with understanding them. Listen to live speech, repeat words and phrases, even if you do not understand their meaning; your brain must get used to the sounding of a foreign language and to you pronouncing its sounds; look up unfamiliar words in a dictionary. The same refers to reading: look for some easy-to-read books and brochures and read them aloud (if you are not studying Chinese or Japanese, reading should not be a problem at all, given that you already know the alphabet). Write short compositions and ask your foreign acquaintances to check them; if you do not have friends native in the language of your choice, use apps like HelloTalk to find people interested in studying foreign languages. Try to think in short phrases in your chosen foreign language. And the main secret: be persistent.