The best way for and individual to know if they are pronouncing a word correctly is to learn the International Phonetic Alphabet, or IPA. Nearly every word in every language can be written out using the phonetic alphabet, which will describe how the word is pronounced.
The IPA is an alphabet that is used to standardize all of the sounds in oral languages. It was created in 1886 by the International Phonetic Association, which was led by a French linguist named Paul Passy. The alphabet has a single notation for every sound found in languages, and it currently consists of 107 letters with 52 letter modifiers. The alphabet has single characters for sounds in that can only be made up of two different letters, such as "th" and "sh" in English, and it has no redundancies, which means that there are no two letters that sound the same, such as "s" in sent and "c" in cent. Similarly, no letter in the alphabet will change sounds based on context.
The IPA is able to write out nearly every word in spoken language. This means that individuals who are confused over the pronunciation of a word can find the word written out in the IPA to learn the accepted pronunciation.