Throughout my gaming career, I've heard numerous horror stories about how a player decided to be an asshole and ruin everyone else's fun for one reason or another. Luckily, I've only had a game ruined by a bad seed a handful of times and I was able to handle them with relative ease.
However, those situations did teach me an important lesson that I like to call the "Golden Rule of Gaming." Its a very simple rule that I believe can fix a lot of problems that people have at the gaming table. Here's the rule:
Don't play with dicks.
That might sounds like the most obvious rule ever to some of you, but you'd be surprise how many people don't follow it. A majority of the problems people complain about can easily be fixed by not playing with a dick.
For example, the complaint that wizards can do everything can easily be handled by not having an asshole who will take those spells that invade on another player's niche. He might carry a scroll of knock just in case they get into a tight pickle and the rogue's player is having some bad rolls, but he's not going to purposefully step on the rogue's toes each chance he gets.
Now, I understand that some situations make it harder to control which people you end up playing with (like at a Pathfinder Society event or playing at a convention). That's a much harder situation to handle and the best advice I can give for that is to try and get through the session as peacefully as possible and do your best to avoid future sessions with any problem players.
However, when playing in a home game, do yourself a favor and try your hardest to not play with dicks or be a dick yourself.