I just realised I did not give concrete examples on how to play Pac, so here we go!
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If you want to play a character, you obviously have to know what the moves do and when to use them, so that's the first step.
Jab: It's an ''emergency'' move. If you don't have time to do anything else without being hit, you jab. You can shield too, but could get grabbed for it, and jab beats grab, so it depends on what you think the opponent will do. It's also nice to just throw as a quick hitbox if you think you can get a hit but only have a short time to do so. Use it after doing moves with a lot of ending lag like dash attacks. That's true for almost every jabs, but this one is generally a good one so don't be afraid to use it.
Tilts: Use them in a similar way you use the jab.
Dash Attack: Really good, just don't abuse it. Mainly to punish landings, and it's excellent at doing that. You can combo stuff from it.
Nair: OoS, Get-off-me in the air, and edge guarding tool basically.
Fair: Spacing, combos.
Bair: Can kill, can stagespike.
Dair: Meh.
Uair: Combos or follow ups.
Smashes: Killing and punishing.
Fruits: You have one for almost any situation. You can either choose the right fruit to deal with a situation easier, or change your playstyle a little, according to what fruit you're trying to use. It can do it all; zoning, killing, edgeguarding, annoying in general, racking up damage, almost anything you can think of, etc.
Trampoline: Stage control, recovery.
Hydrant: Huge stage control, killing, helps landing smashes.
Pellet: Killing, recovery.
Throws: Meh. If you can get a free grab might as well do it, but it's not amazing either imo. Doesn't really kill or combo reliably, but it gives you time and does damage which is always great. It's not bad, but you won't be using it as much as other characters.
Crawling: Okay, it's not a move, but Pac's crawling is by far the greatest animation from any smash game ever. I use it to taunt, personally.
This is very summarized and in no-way exhaustive. It's just what you
GENERALLY use the moves for. Generally is the key word here. I started writing an in depths explanation, but gave up halfway through the first move because reasons, whatever.
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You can see there's two kinds of moves: those who kill and those who don't. You want to use those who don't kill to get up damage and eventually land the kill moves. That's smash in a nutshell, and Pac is not different from the other characters in that aspect. Note that while kill moves are usually riskier (but not always), you can use them to do damage in certain situations.
The kill moves are (At acceptable percents. Eveything can kill at high enough percent, but I'll just list those you should be using the most): Nair offstage, Uair high enough, Bair when you're close to the blastzone or can stagespike them, smashes, some fruits (Orange, Apple, Melon, Key. Bell is pretty much a guaranteed kill when you hit with it at high percents if you follow up, but it doesn't kill itself), Pellet, Launched Hydrant. Throws too I guess if you have the right conditions.
Everything else should be used to either rack up damage (through combos and follow ups), or gain stage control so you can be safe and not get killed/hit with the other moves. Almost every move can do at least two of these three tasks (Killing, Damaging, Stage-control). This is why Pac is fun to play, and it's also why everyone tells you to mix everything up. You have the privilege to be able to use a move in different situations, or different moves in the same situation. Use it, because a lot of other characters can't.
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Hydrant is one of your best friends. It basically cuts the stage in two for several seconds, so it can give a lot of relief against campers/rushdowns. You can use the water simply for pushing away people, or with your smahes. The samshes stay active for long, so if you do them while being hit, it kind of extends your range a lot. They do nice damage and knockback and can therefore be used as kill moves. They can prevent getting gimped/attacked in the air if you drop them, because they stop you for a moment and generates a strong, long-lasting hitbox below you. I feel like this is the move that defines Pacman.
Fruits are great too, but it would be too long to explain them in details. Just learn what they do and have fun with them.
Trampoline on stage forces the other player to go around it by jumping, or it makes them jump if they walk on it. This completely cuts rushing down, which is a Pac weakness. Since the opponent has no choice of going in the air, you know where they will be and what they will be and what they will do next, which is a HUGE advantage.
The force of these moves comes from using them simultaneously.
The Hydrant and Trampoline (I'd add fruits in that) are great by themselves; however, they become exponentially better when used together.
This is so true. You can control the stage so you can control where you want the other player to be in a way. This means you can play more safely if you need to, and it's easier for you to damage them and land the kill moves. The B moves are the basis of Pac's gameplay.
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Okay. I can't really say much else, because that's really what Pac's gameplay is after all. Another tip I can give is don't do stupid stuff. I don't know how to phrase it otherwise. For example, don't drop a Hydrant randomly because you can. Will it hit your opponent? Do you need to push the opponent away to prevent a certain thing to happen (Villager sapling camp, rushdown, etc)? Do you need to launch it to kill? If you answer no to those questions, don't do it. It will just give a powerful tool to the other player.
Another example would be don't throw fruits if you don't have to. If you can't punish shielding/dodging and the opponent can just shield/dodge it, what good is throwing the fruit? The key is the prefect example; it takes 5 seconds to charge (or something like that, I don't feel like timing right now) so if you use it carelessly you'll have to waste 5 seconds to get to it again. These are all logical things, but it's what makes the difference between a Pacman player who knows how to utilize his assets, and one who doesn't.
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That's my take on the character. I know there's other ways to play him, but this is the way I do it. You guys all did a great job so far in the thread, so I tried to keep it more general and not be too redundant. As I (and almost anyone else) said earlier, there's so many options that you can't tell ''How to play PAC-MAN''. You just have to try stuff. If you see another Pacman doing something you didn't thought of, don't be ashamed to incorporate that in your gameplay. That's how the Pac community gets better. We'll get these Rosalinas.