So let's get this started with the fundamental laws of the jungle.
Now then, who I am: I started my gaming life by playing text only MUDs (see: http://en.wikipedia.org/wiki/MUD ) in the 90s and played UO as my first graphical MUD. I played EQ1 on Rallos Zek back when it was EQ's only "red" server. I played Star Wars Galaxies pvp as a per CU Jedi and lost my character forever when he died. I played L2 on and off for a while until Eq2 pvp caught my attention. I was mediocre at best, hardly a feared PKer, but I learned to survive and enjoyed what I played, no matter if I was outmatched or not. I understood what I was playing.
Law of the Jungle #1: You are going to die.
There's no getting out of it. You did not come here to be safe. You were safe before. Now, those strawberry fields of treasure and experience are crawling with cutthroats who know where you used to go, what you used to do, what you used to seek there, and how to use this knowledge to catch you and inflict death on you. They aren't going to wait for you to get ready. They aren't going to play fair. They aren't going to care if a particular move or tactic is too devastating if they catch you with it. Your only way around it is to learn them- learn where they are, learn what they're after, learn what they're going to do, and prepare yourself ahead of time. And no matter how well-prepared you are for what's out there- you are still going to die. There is no way out of Law #1. Whether it's at the hands of someone at the top picking you off just because you're there, whether it's a group of players lower than you who gang up and tear you apart, whether it's an even-con, similar class who just happens to get that last shot in before you, whether it's some punk who sucker-punches you right after a tough fight, or whether it's someone whom you thought had no chance in hell who happens to get lucky, you're going to be killed. If this bothers you, you made a mistake.
Law of the Jungle #2: This isn't a PvE server
You can't play the same game you played when they weren't after you. The skill and tactics that were good enough before because of its effectiveness against the mindless MOBs isn't worth squat- you have to outfit yourself with your most dreaded foes in mind being actual players who are out to kill you. You can't just trot over to your favorite hunting grounds to knock out that quest anymore and hope for the best. They know that those spots attract people who still think that they're playing the same game, and they will be waiting for you. (See Law #1) You have to forget everything you learned on the PvE servers, and be prepared to learn it all over again. There are new rules for how to get a level. There are new rules for where to hunt, and there are new rules for which routes to take through the lands. If it's something that many people used to do or where many people used to go, it is now bait that will lead many people to their deaths. If you thought that you were going to play the same route you played before on PvE except that you can kill people now, you made a mistake.
Law of the Jungle #3: Cover your rear
All players have advantages in certain situations. If you find yourself in one of these situations and you aren't the player in question, see Law #1. So, such-and-such can take you down solo if they get the jump on you, if all they do is X and Y? Well, yes. That's what they do, and you were there. The essence of pvp is that all players have advantages and weaknesses, and the way you overcome these weaknesses is by grouping with someone who can complement them. You're not here to run around solo and have a fair, balanced even 1v1 match against everyone you meet. That's not PvP, that's dueling. Running around alone isn't something you have the right to do. This is not, nor should it be, a game where you always stand a fair chance. There's more to PvP than who has what nuke or how many hitpoints or what dps rate is. PvP is about knowing everything you can do and how it works, not just what numbers popped up when you fought mobs before. If you can't fight them, learn how to. If you can't learn and expect others to change everything around to suit you, you made a mistake. Learn, Adapt, and Grow; if you can't do that then you're not cut out for this.
Law of the Jungle #4: Success is measured by survival
Any idiot can PK another, that doesn't make them skilled. Your skill isn't determined by how many people of what level you can take on. And the little punk who ran away, or avoided you altogether, he's not a coward, he's smart. Just because you pvp someone doesn't mean you have the right to kill them. You have to earn that kill. If they get away, they survived. If they fight back too hard and you're outmatched, sticking around and letting them have you isn't brave or honorable, it's stupid. Make them earn it! If you can get away, you deserved to. If you can't out-damage them because they are jumping around and dodging your attacks, it's not unfair- they're just thinking ahead of you. Don't lower your defenses just because you think that extra bit of dps that you used to get against mobs is going to turn the tide- because you're thinking in terms of a kill you haven't earned yet and not thinking with survival in mind. It takes time, patience, and smarts to figure out all the little tricks, tactics, and moves that help you survive in PvP. It's not about killing- it's about depriving your enemy of the kill. If this isn't your primary thought when planning every last detail of your character , see Law #1. You aren't a good PvPer because of who you fight and which fights you win, you are a good PvPer depending on your overall level of preparation and how many times you can count that that preparation saves your rear.
Law of the Jungle #5: You are never going to be a God
Too many people have those cute little adolescent fantasies about being a powerful, unstoppable killing machine with the title of "Overlord" while wielding the shiniest, largest and most phallic weapon in the universe and laying out every single foe you happen to encounter through sheer invincibility. It ain't gonna happen- ever. (See Law #1) PvP isn't for people who like to play single-player games in godmode. You didn't come here to be godlike, you came here to embrace mortality. You aren't just here to kill other players- you came here to give them permission to kill you, to utilize advantages over you, to take advantage of your weaknesses, to leave you broken and bleeding while they dance on your corpse. If you came here planning on becoming the all-powerful king of the hill that no one can topple, you made a mistake. Coming here means the players are going to be after you more than ever. You will never be safe again. The safe servers are still where you left them.
Law of the Jungle #6: It's still just a game
Playing on a PvP server doesn't take supreme courage or large testicles. It doesn't take an iron will, or an asbestos stomach. It doesn't make you a man. You're still a geek just like the rest of us, it's just a lot more difficult. If it's too hard, too frustrating, too unfair, too immature, too cutthroat, too inconvenient, or if you're just not that good at it or if you think that so-and-so shouldn't be doing such-and-such because it "ruins" your fun, then it's not for you. You're here if you enjoy what you're playing. PvP is what it is. It's MEAN. And if someone PKs you and dances on your corpse while you are on your way to turn in a quest, or whatever else it may be that spoiled your plans, well, you either suck it up and keep playing or you're on the wrong server. It's only "griefing" if you let it give you grief. If you can't laugh it off, you're the problem. If you're not having fun, you made a mistake. There is no shame in playing on the PvE servers if that is more your cup of tea, we're all here to play games, and the game you play isn't a reflection on your status as a human being. However, PvP is a different game. If you could go live in a beach house with central air and a plasma-screen TV for the same price, why would you move into a shack with no plumbing or power and complain about the leak in the roof? You have to want to live in this shack. Don't expect them to turn it into a Carebear resort, they've already built those for you. (PvE servers)
There is only one thing that should be on your mind when you think about all the problems with PvP. The final, and truest Law of the Jungle:
Law of the Jungle #7:
You can't spell slaughter without laughter."