It all depends on how it is being used in a sentence. Here are some examples of how it is used with and without the article: Without: "If you're not sure, it is best not to say anything" "I am at my best (or "feel my best") in the morning" With: "He is the best player on our team" "The pool was the best part of the hotel" "This is the best chicken I have ever eaten" If you would like to try making some of your own examples like this to make sure you understand, please feel free to add a comment and I will reply to tell you if they are correct.

When you use "the", obviously a noun must follow. The superlative is describing a thing. When we don't use "the" with a superlative, you'll notice that the superlative describes a verb.