How do you say here comes my friend Juliette in French?

There are a couple of ways to say "Here comes my friend Juliette" in French, depending on the context and formality:

Formal:

* Voici ma (bonne) amie Juliette. (Here is my [good] friend Juliette.)

* Voici mon amie Juliette qui arrive. (Here is my friend Juliette who is arriving.)

Informal:

* Voilà mon amie Juliette! (There's my friend Juliette!)

* Regarde, c'est Juliette! (Look, it's Juliette!)

* T'as vu, Juliette arrive! (Did you see, Juliette is arriving!)

The best option for you will depend on the specific situation.