I consistently observe people who aren't meeting expectations. I will take 20-30 minutes to observe them ringing, sometimes I'm more subtle than others. In that time, I'll count the number of guests they helped versus the number of times they've mentioned the REDcard. Say in 20 minutes, you had 15 guests. If I observed you ask 14 of the 15 guests about the REDcard, I'm probably going to let it go. If I were to observe you asking 3 of the 15 guests about the REDcard, I'm going to pull you into an office and coach you for it.
It's a horrible system, and the entire REDcard process needs to be redone from scratch. I've been in sales and sales management positions and the REDcard goals are very high and unrealistic in comparison to all of my past positions and experiences, but I can say that every single under-performing cashier that I've gotten rid of was due to them not talking about the REDcard. There are plenty of people who don't get as many redcards as I want them to that are not performanced out, but the one's I eventually term are always the ones who not only don't meet redcard expectations, but don't ask about them either.