The activities should be directly related to your "I Can" statements and should practice a target skill. My boards are divided into: Escucha, Lee, Habla, Escribe, Mira, Toca, Crea, Dibuja, and Cultura. There are 9 because the pocket chart I bought at Walmart had 9 pockets. It wasn't a magic number. The activities should be things they can do in the down time after they finish any in-class work, although sometimes I do a few things they can do at home. With this, there is no reason to have students with nothing to do because they always have choice boards!
My students know that they have to do 7 choice boards per unit. Typically, there is a rush on the choice boards the first day and they all take pictures of every activity and decide later which ones to do. On the right side of the folder I have the task. I make it business card size and repeated so that my students who don't have technology can just tear off one of the cards. As I said, most kids just take pictures of what the need.
I put Unit 1 CB 1, U1 CB 2, U1 CB 3 etc. into the grade book at the beginning of each unit and leave them blank. You can't name them the skill in your grade book because not every child is going to do every skill. I tell the kids to make sure they have the title, the date and which number it is for them on the paper they turn in. That way I know which one it is, and they are responsible for keeping track as well. I mark it for effort/completion not accuracy because it's practice of the skill, and put it in the book as a running total. At the end of the Unit, I put zeros for all the ones they didn't turn in, and their grade is affected accordingly.
If you have multiple preps, you can use each column as one prep and they can choose 7 of 9 activities to do in their column. The picture at the top shows this option, with a column for 6th, 7th and 8th grades. I strongly recommend color-coding the folders (or the labels on the folders) so that the kids know which column is for them.
If you only have 1 prep, your life is awesome, and you can do choice AND differentiation with this tool. The administration likes differentiation. :) Last semester the three columns were all for SPA I only, so I divided it up like ski runs and had green circles, blue squares, and black diamonds to show the levels of difficulty. The kids still only had to do 7 of 9, but this time they had to do AT LEAST 1 from each column. By requiring that, I knew that all the students were challenging themselves at least a little bit, and the more high-flying kids could do harder work if they chose.
Once you get to the end of your semester or year, you can make a "best of" version of choice board activities for your review week. You could create new activities for them to do, but at the end of the year that seems like a lot of work. Personally, I just mix up the ones from the previous units and use them as in-class activities at stations or for independent work while I work with small groups or individuals. My students are doing mix-it-up choice boards for the two days while I do individual speaking tests. It really helps me, because they don't need me to do choice boards, so I can get through the speaking tests with minimal interruption.
Hope this helps! Happy creating!