I think just watching the shows makes you a viewer. IMO, a Trekkie is more involved with Star Trek, mentally, physically and/or emotionally. Knowing detailed knowledge of the Star Trek cosmos, having a deep fandom, dressing up to go to conventions, having a collection (videos, props, etc.), speaking Klingon as a language, contemplating episodes to help guide you in life, letting it direct your moral compass, even some go so far as to treat it religiously. I think those are the true Trekkie.