There are at least 100 words which are the most commonly spoken words in the English language. You can determine these words by listening to conversations, guessing from your experience or consulting a source like YourDictionary.
According to the The Reading Teacher's Book of Lists, the 100 most commonly spoken words in English are:
The list of most common words quickly enlarges to over 500 words when you add the most common words used in British English and Australian English to the list of common words in American English. These 500 words were, in turn, ranked in popularity by world-english.org using surveys of contemporary newspapers, magazines, books, tv, radio and conversations.
While there are many words that you may use frequently at the top of the list, there are also many words that you may not use as much throughout the list. For example, the words "correct," "develop," "produce," and "fact" all made the list as well.
One of the ways you can track the words you use most frequently is by keeping a journal for a week. By writing down or recording every word you say, you will begin to see the pattern that surrounds the context of your words.
You can do this exercise off and on for two months and then take time out to review the words your have recorded. Notice how many times you use certain words. Then you can easily refer back to this list of the 100 most frequently used words for review. Notice how the words that you say correspond with the words on the list.