Appart of the default ports and correctly configuring WPMS...

In the Advanced Tab:  
![MAMP PRO][1]

And manually add the subdomains in `/etc/hosts`<sup>1</sup> file:  

    # BRASOFILO MULTISITE START 
    127.0.0.1 test1.brasofilo.dev
    127.0.0.1 test2.brasofilo.dev
    127.0.0.1 cloned.brasofilo.dev
    # BRASOFILO MULTISITE STOP

<sup>1</sup> *The folder `etc` is at the root of your HD and it's hidden. You can open the file using TextMate or with your FTP client (enabling `Show hidden files`). It can also be done with the Terminal, but I don't use it for that and you'll have to search How To...*

  [1]: https://i.sstatic.net/F9ZKM.png