Make sure to have the words to all of the songs available either in the printed service itself or on a song sheet. In addition, have sheets with the transliteration of all of the Hebrew used in the service available so that everyone present can follow along, whether they know Hebrew or not. Remember, the goal is to create community, to help everyone feel included. When putting the service together, you should follow the normal order of the prayers. You can then insert various readings between the prayers.
Readings can come from other prayer books, poetry, or other books.
You might want to have a theme for your service and base your readings around that theme. If you decide to create a siddur for your community, consider having multiple options for readings for some variation.