The definition of apostacy is simply not believing any of the entire spectrum of JW teachings, or anyone who disavows the "faithful and Discrete Slave" as God's sole agent on earth. I don't have it handy ,but someone here surely has quotes like this. In other words, never express your doubts. Seriously, don't. If they want to meet with you say you're too busy. If they show up unannounced tell them to call next time first. It is all up to the determination of the Elders and their interpretation of the WT.