In this game, you control an odd, yellow insect who flies backward (with his wings to the front), or perhaps a strangely rounded pair of hedge-clippers. Notice that in the session shown here, we're steering him away from the undersized squid with whom he shares the maze. Avoiding them is an excellent strategy, and it should be applied as often as possible.
If your character collides with any of the squid, who are apparently very hot to the touch (in spite of the blue, watery environment), he melts. He's then replaced with an identical character, and you have one less turn in the game. Normally, you begin with only three of these; however, you can change the machine's dip-switch settings to give yourself more turns. This is another highly recommended line of attack. I had to stumble upon it while using an emulating program called MAME; for some reason, the tip was never mentioned in the magazines or strategy guides that were released during the game's early years of popularity. I can assure you that you won't see such half-researched writing here.
Curiously, the squid all turn blue, lose their ocular functions, and duly appear rather distraught whenever your character devours one of the flashing circles in the corners of the maze. The reason for this has never been discovered, to my knowledge; and if any of the game's designers know, they sure aren't giving it away. (I've tried to contact them, but I've repeatedly met with Japanese cursing.)
In any case, it's still important to stay away from the squid. Plowing right into one while he's looking so upset can't possibly be advantageous. In fact, you might even lose two turns, rather than just the one. A blue squid is not in a sociable mood. After all, they're not suddenly avoiding you for nothing.
As you can see here, an actual food item occasionally appears just below the underwater cave of the squid. Perhaps it's mischievously dropped by the enigmatic, never-seen "Pac-Man" entity after whom the game is titled. This food must obviously be left alone, as your character clearly likes only items with rudimentary shapes, such as the dots and circles. See how he closes himself to the world when he winds up anywhere near real food.
All of the best players know the real secret to any video game, which I'll repeat here: Avoid ending your current turn. While watching anyone play most any game, it occurs to me that very few people seem to have discovered this tactic.
There are graphical glitches in the game: two wide gaps in the walls to the extreme left and right. One can only marvel at the fact that the designers didn't take time to correct these bugs in revised versions, especially given the game's immense popularity upon its release in 1968. What's even worse is that far from being eradicated in Ms. Pac-Man, the sequel, these mistakes were more numerous! And don't get me started on the incomplete surfaces in Donkey Kong.
As the missing wall-graphics were obviously not intentional, you should stay away from them. It's pointless to risk a complete malfunction of the program. I once witnessed a player accidentally moving his insect/clippers through one of these breaches, and his character skipped to a distant part of the maze! Precarious glitches indeed.
Keeping all of the above tips in mind, the absolutely worst thing you can do is
to consume all of the dots and circles in the maze. Every single one of them
will be replaced, and you'll have to start all over!