I consider myself in between that range of complete noob to skilled, but having not played for as long as a lot of people, I try to help people out new to CF. I think most players can get to at least my play level a lot quicker than I did with a little help and some friendly advice.

Flee quaff in bad fights is your friend. Always carry two teleport potions in your inventory. If the guy sits there and sends you tells like coward or something, just ignore them. I hate when players get annoyed for you not fighting them on their terms. Fight battles you have a chance at winning, dying is fine, but don't make it easy for other people to kill you by fighting when you should flee. Not many people have the role of I want to be the easy target that just gets killed all the time. You char should have a survival instinct. He should actively try to avoid dying by any means necessary. When you're solo, this applies almost all the time. There is something to be said for trying to save group mates and such, or defending cabals, but walking down eastern and getting bashed by a giant sword spec you are not ready for, your first command is flee, your next is quaff.

As to midbie PK, it is arguably some of the hardest. At low levels most people are generally weak, though some amass ridiculous sets and just terrorize those ranks. But it is relatively easy to rank out of those ranges. At mid levels you have people that are at the height of their power curve a lot of times, like sword specs, that just tear it up. By hero a lot of things tend to level out again. A vet can tear up the 30 ranks a lot of times and become far less deadly at hero. A sword spec fights the same for example, pretty much from 32 to hero. Legacies help keep him competetive again where as at 40-43 warriors often get tooled hard.

A shifter may have a hard time at those ranks, but with their final form all the sudden kills them easily. I think the greatest game balance exists at hero actually, though game knowledge will still favor vets. Unfortunately, the only way to get this is to play and not get discouraged. I'd say almost every vet out there probably still learns one new thing with every char they play. That's how big and complex CF is, and part of its draw. It's never the same game twice.

I'd say also learn how to define success in CF not by PK stats but by enjoyment you get just from playing the game. If you're playing a fun role and having a good time exploring & learning things, getting wiped in a PK won't even be noticed. And if you play as a friendly guy with a reputation for not being douchey, most pk's will leave you your stuff. Just cause you lose 2 or 3 pieces after is not a reason to go bitch to the killer. If you take it in stride and show a little class, you'll find that person will probably leave you alone for the rest of the log in and not make a point of looting for no reason in the future. (With the caveat like in all multi player games there are jackasses around and them you just have to deal with and ignore)

Also, realize vets don't know who noobs are, at least not at first, so will treat you as anyone else based on what you are playing. (I.e. I play an orc and you an elf, I'm killing you or trying to most likely on sight) However, once they do realize you are newer they tend to become more helpful to you. I might in an IC way try to suggest a tip that might make you able to survive, or even beat me in a future fight.

Playing a utility build is best for learning CF. As was said, assassins are great. Bards are too. Certain shifters, and certain defense based warriors. All are great to learn CF with. The real key is to play with eyes open so you are learning. Playing a rager that just runs the circle of eastern voralia and galadon is not really going to teach you all that much except maybe how to run certain places. Playing an explore herald where you pay attention to where you go and what people do can give a lot of game insight.

Of course, talking to people IC is ultimately the absolute best way to learn anything in CF. Might take five tries to find someone to help out, but when you do, you can learn in five minutes what others might learn in the course of an entire char life. It's not that game knowledge is secret, it's just that you have to put in the effort to acquire it. Help files are starting points, the depth of knowledge vets have is really derived from them doing things and learning from them. And a lot of time a vet becomes so not by having played 95 characters but by having played 4 or 5 really good ones and being attentive to what happens around them. Their experience is your gain a lot of times. I could sit on eastern as a rank 1 for a few hours, and just watch PKs and learn a lot about how classes work and favored tactics. What moves do they use? When do they flee? Why do they flee? Why do they remain? You can read logs too and learn a lot, and sometimes people's comments actually do provide useful insights into the mechanincs of the fight and suggestions for improvement.

Ultimately the best way to get good at CF is to not reinvent the wheel with every char, but build upon what you already know and try to improve upon it each char.