Perhaps the members all have preschool children, maybe they all belong to the same church or religious organization, or perhaps they are neighbors. By beginning your group as a spinoff of another affiliation, you already have two things in common which may make club rules easier to establish. If you do not belong to another group, you can simply seek scrapbookers through other sources such as your local scrapbook store, your local scrapbook supply representative, your library, your town hall, your YMCA, the grocery store bulletin board, or even online. Several years ago I helped form my first scrapbook club by posting a notice on a scrapbook bulletin board online. Once you have a few interested scrapbookers, have a planning meeting to decide how you want to establish your club.
Some clubs begin with a set of rules while others just gather informally on an occasional basis.
If you want your club to meet regularly, some rules will be necessary. If the club will meet in homes, establish how to rotate so that it will be fair to all members. If the club will meet in a community center or other facility that charges a fee, decide if dues will be necessary to cover this expense. If so, decide if you will allow all children or just those old enough to crop. If babies and small children will be allowed, decide if you want to pool recourses and establish a nursery or babysitter.