From the mailbox:
After reading your explanation on the use of "it" in Spanish, I saw this expression on a Spanish-language website advertising a women's tennis tournament:
Lo mejor está por llegar.
I took it to mean: The best are coming. I was just wondering why they use lo here instead of la or el?
Whenever you see lo before an adjective, you're seeing that adjective used as an abstract noun that doesn't refer to any concrete thing in particular. So lo mejor doesn't refer to the best of any particular thing. If we were referring to the best player in women's tournament we might indeed use la mejor, or if we were talking about the best match (partido) in a tournament, we might use el mejor.
But lo mejor means "the best" in an abstract sense. We might use is in a phrase such as lo mejor de Hollywood (the best of Hollywood) or lo mejor en deportes (the best thing in sports), or even standing alone: ¡Es lo mejor! It's the best!
The best translation for the sentence you gave is probably "The best is yet to come." The phrase "Lo mejor está por venir" is also very common and means basically the same thing.