Back in the day it was combination of being young and paying attention to the basic patterns of the ghosts, then keeping a count of dots eaten so you could know when fruit was going to appear.

Each ghost has a set behavior in each phase of a board, plus a different way of picking where to go. The red ghost is always trying to get to where you are, but pinky is trying to get ahead of you. I can't remember all of it any more, it's been over thirty years.

Back then, it was all a bunch of kids spamming quarters and figuring things out as best we could. I wasn't the one to figure out the patterns, I was just good at using them. And my hand/eye coordination was fast. So I could see the ghosts and where they were going, then adjust my movement before it would be a problem.

Staying ahead of the "ai" of the ghosts was the only real way to get past around lvl 50. Before that, you could usually just clear a quarter of the screen while avoiding them reactively. After that, if you weren't able to visually track all 4, and have a sense of where they were going to be, you'd eventually crap out, or lose fruit, which means a lower score.

There's articles out there now that give details I had no idea were part of it back in the arcade days though.