I just played through Metal Gear (NES) again for the first time in ~23 years. A good game. What I don't understand though, is that it seems as though we HAVE to go through the mazes in the game in order to complete it and I can't remember finding any information ingame on how to get through them. Is that correct? We HAVE TO go through the mazes AND there is no ingame information about the correct path? Just... trial and error?
There was no answer in the game for how to solve this maze. This was confirmed by someone in 2009 who dumped all of the text from all of the transceiver messages just to try to answer this exact question. The original Metal Gear on the MSX didn't include these mazes and they seemed to be added to the NES version without any additional clues. However this maze like the one in Zelda (which did have an in game hint) weren't incredibly difficult to solve through trial and error. At the time I remember trading hints with other kids at video rental stores and at school to get through this. Swapping through all 8 cards seemed more of an annoyance with this game.
I think the majority of people who couldn't figure this out and didn't call into the Nintendo Power Line (which activated just in time for this release) used Nintendo Power Issue #3 where this question was asked in the Counselor's Corner. You either subscribed to Nintendo Power then or had friends who did back then. The exact question in this issue was "How do I get through the maze zones" with a detailed answer.
This issue came out in November 1988 after Metal Gear released in June 1988 in North America. So it was just in time for kids who had either given up or were just about to get this game for the holidays to not get stuck on this.