Today's post is probably a regular tool for many, but I've come to realize there are tons of parents and teachers who aren't aware of a device for counting frequency: the tally counter!
This tool can be purchased from Amazon or at most sports stores. They're notably inexpensive ($1-4) and typically come with a black lanyard for use. With the lanyard, the tally counters can be clipped on a key ring, belt loop, or worn as a necklace. At the end of a day, session, time period, or interval the number on the face of the tally counter can be transferred to the data sheet.
Additional colored lanyards (shown above) can be purchased, too; this is helpful in situations for tracking multiple behaviors or multiple students.
I prefer tally counters because they are a tool that is inexpensive and reliable. They don't use batteries and, when worn, travel constantly with the individual collecting data. Tally counters may also prevent some errors in data for those moments when you're thinking, "Oh, I'll remember to write that incidence [of behavior] down." (Come on, we've all done it at least once.) In addition to all of this good stuff, they're nearly indestructible.