Having led a few children's book clubs over the years, I think the most challenging thing involved wasn't prepping materials, having discussions or choosing books, but setting up the date and time! Everyone's schedules seem so hectic these days that it's often difficult to find a date and time that works for most people. Once you do that, everything is easy!
First, what kind of book club do you want to have? You could have it centered on a theme, like fantasy or nonfiction, or you could leave it to the kids to suggest books each month. Ensure everyone knows each month's book a month in advance so they have time to read it. This means deciding each month's book on your monthly meeting date!
Next, decide if you want to do anything other than simply discuss the book. Do you want it to be the book plus a craft, a game, or another activity that fits the theme? Maybe you want to make a food around the theme. Here are some more ideas.
Have you started a book club? What tips do you have?