A Spiritist meeting is a "collective being whose qualities and properties are the result of the totality of its members." item 331 -  [The Mediums Book, Chapt. XXIX, item 331] - Allan Kardec

Three Types of Meetings.

1 - Frivolous - participants regard spirit manifestations as an amusement, no serious results, frivolous questions and conversations
2 - Experimental - production of physical manifestations 
a) for the curious - non-instructive
b) for the serious - study of the laws of the invisible world
3 - Instructive - research and study of Spiritism and its doctrine; instruction regarding morality.

What we want: Qualities of an Instructive Spiritist Meeting 

- a grave and concentrated mind
- a perfect community of views and sentiments
- reciprocity of kindly feelings among the members 
- abnegation of every sentiment contrary to charity 
- a general desire of the truth
- exclusion from the setting of everything of frivolity
- concentration of thought and desire in the pursuit of the common end and in the evocation of the spirits whose presence is desired
- cooperation of the mediums, with the disinterested desire to be useful, without vanity, ambition, or any other selfish motive

(Reproduced from the GEAE's website with permission from the author and from the editor)