I'm probably the odd one out here but I recommend against using any viewing guides. I think watching "bad" episodes/movies, and finding out why they're bad, is part of the experience. Seeing Worf angrily smash a lute against a tree, a 60-year old Uhura perform a "seductive" fan dance, Janeway and Paris turn into newts and Quark become a tranny for fun and profit is a big part of what makes being a Star Trek fan so much fun for me. A lot of nice character interactions are hidden away in the lesser episodes as well, so if you skip too much it will inevitably diminish your understanding of the characters.
I half agree with you. But viewing guides *are* still somewhat useful, both for getting new people into Trek, (Because let's face it, there are a lot of bad Trek episodes even in the good shows, and a lot of them tend to be early on.) and also for skipping the bad stuff as a seasoned fan while re-watching (If you can't be assed to remember what the good and bad episodes are)... But I do believe that if you end up becoming a Trekkie, it's worth going back at some point and seeing everything.
Except for STD, and I guess now Picard.
Side note,
@MembersSchoolPizza 's rundown of all the various iterations of Trek was fairly on point, but I wanted to weigh in about the movies:
I never liked the whole "Even Trek Movies are good, Odd Trek movies are bad," line... (Even before Nemesis utterly sank that notion.)
I'm not the biggest TOS show fan, but I would actually say that all 6 of the original TOS movies- Including both Star Trek (I): The
Slow Motion Picture, (my personal least favorite of the 6, and the one I would say to skip if you were going to skip any.) and Star Trek V: The Final Frontier (The one that most people hate, and even I will qualify as "So bad it's good"), are worth watching at least once.
"Star Trek III: The Search for Spock" is a good movie, and an essential watch if you actually care about the overall story of these films, as it's the middle part of an otherwise well-written trilogy. It just has the misfortune of being sandwiched in between Star Trek II: The Wrath of Khan, (One of my personal top 5 favorite movies of all time.) And Star Trek IV: The Voyage Home
i.e. the one with the whales... Which is a hella-dumb fun stereotypical 80's movie that a lot of people
who aren't me love more than anything... (Ok, so I don't like it as much as most people seem to, but I still say it's worth watching... And there's a decent chance you'll like it more than I do...)
Fun fact: The (pedo) dad from silly Christian show- 7th Heaven was a major character in Star Trek: The Motion Picture, and the (probably not pedo) mom from same silly show 7th Heaven was the
Bond Kirk girl in Star Trek IV... Funny coincidence if you ask me.