Choose a good title and description

The most important fields in the public tab activation are Title and Description. The title will be shown on the top of your public tab, as a part of the URL to your public tab, as a title in the metadata and will affect greatly Google ranking and how it will appear in Google results.

You can always change the title at a later stage, every time you do it, it will change the URL.
Note that you might lose all your Facebook likes and Google+ +1s when changing the title also.

A good title is a specific title, but not too long. Think what would users search on Google to end up on your public tab.

Good title examples:
Everything about PS4
Sites for movies reviews
All employment sites in US

Bad examples:
PS4
Movies
Employment Sites

Descriptions helps users understand more in detail what is your public tab about, it will be stored in the meta-description and also has effect on how people can find your public tab.