You should include the group name, description, type, Web site URL, manager e-mail, whether you want people to automatically have access to join or be pre-approved by you or another manager, and whether you want your group visible on your member’s profile pages.
If you’re wondering what to write for your group description, first click the Groups Directory tab near the top of the page (before writing anything) and read through similar groups in your group type. Then, go back to the Create Groups page and enter your description. (If you check the Groups Directory while writing your description, you’ll lose whatever you typed.)