I did play on an Atari in my very early youth in the late 80's early 90's, but my gaming "career" (if you like) didn't really get going properly until the mid-late 90's. There were magazines and the Games Master TV show, but knowledge of what games were good and bad as well as tips and such spread largely through word of mouth. Kids in school would pass around what they knew to thier friends and so on. I suppose the same thing happens online today just on a much larger scale with user reviews, user scores, social media and, not forgetting, internet forums.
It would have been even worse for kids in the 70's and 80's because there was no real way to tell what games were good and games were what bad. Video games were just perceived differently as well. They were toys back then, so a review of a video would be taken with all the credibility of a review of a Barbie doll. Even when there was reviews of a game, the market was so saturated that only so many games got coverage. So yeah, that was the dark ages. The popularity of arcades were also a factor, the was just not as many people playing games at home. Still, even then, there was word of mouth, but that was really about it.