Thought I'd share my few little ideas about roleplay which might answer your questions. I've been roleplaying for a long long time now across a lot of different games and I can't imagine playing an online game any other way. It can be a lot of fun and it opens up a whole new side to any game, which might be worth visiting at least.
So what really is roleplay?
I guess whenever you approach a game like TERA, you can see it in two different ways. One would be that your character is just a means to an end. It does not really matter what it does, how others see it or how it looks like for that matter. It is there to get you somewhere, probably for you to level up and it is more of an aspect of the game itself, something necessary to play the game, an object within a game.
The second take on this would be that it is not an object, but your character can have a personality. It is a part of the world in front of you, it explores what the game has to offer, immerses itself within the story and in fact, it may have a story of its own to tell.
These two 'views' are obviously not strictly separated. There is more of a continuum between what I just described and it depends on you how alive the character feels. Some people will simply overlook the character completely, some will see it as a part of the main story plot the game offers. Some will appreciate the fact that your character is unique, pushing the idea a little further. This may be as simple as buying your character armour just because it looks good, an may be as complex as writing pages and pages of stories with your character as the star.
I myself love my character very much and enjoy playing the game not just because it is fun from the gameplay point of view (which TERA definitely is), but also because it lets me live out something I could not experience outside of a fictional universe. To me it is a little bit like playing in a movie. Have you ever watched a movie and wished you could change things in it, tell the person on the screen to do this or even wanted to explore what is beyond the screen? Roleplaying for me is just that.
Now this is my take on it and I am sure every person has a slightly different reason, which makes the world an amazing place to be. If we all were the same, that would be no fun!
The game itself promotes the idea of roleplay quite a lot. Actually, every RPG does that. The npc characters you meet talk to your character, trying to pull it into the story. The world moves, animals react to you, the economy is impacted by your character harvesting, selling and buying things. Making the game an immersive experience is something the developers focus on quite a lot. So it might be said that anyone playing the game is to some extent a roleplayer! The question should be, how much of an importance do you want your character to hold.
So now you sort of see why you might want to roleplay or push it further. But how does one start, wouldn't it be strange and difficult at first?
As someone mentioned in your thread, a lot of it is imagination. So does that mean you have to sit down and dream up a whole novel about your character before you start playing? Not at all.
Once you decide you want your character to be meaningful, it will come naturally. It is hard to guess what will happen or how things will progress, but generally all you have to do is act out the role. I started TERA with my friend and we made two sisters, knowing nothing about how they are, their personalities, and not knowing anything about their story. We just played the game for a while. As you play, things happen in the world around you that impact your character. You may put in your own views into your character, making it respond to what's happening.
I was handing in a quest and my sister rushed out to attack some tree, which knocked her down. That made an impact, so I ran over to help her. I do not want to see my sister dragged around by some evil tree, do I. :) So I ran over, killed the thing and helped her. I asked 'You alright sis?'. And we roleplayed a bit around that before moving on. Probably the mildest form of roleplaying, taking the games events and reacting to them.
So events in game influence my character, what's next?
People. There are hundreds, thousands of people experiencing their own stories and they are all connected. What most people call 'roleplay' is responding not to the game's events, but to other people.
Again, this does not have to involve thinking up a whole world. It can be as simple as killing a tough monster and being helped by a person, chatting about the fight afterwards (which is how we made our first friends with my sister). You tell them your name and thank, they tell you theirs. You can just chat about the area, the monsters or about the task you are on at the moment. This could be anything from 'Such a terrible creature. Phew, all this to deliver a letter to some guy.'
How to make it more believable, more authentic?
Just like you would in real life. By adding gestures to help you convey meaning. It is hard to guess what a person really wanted to say by reading a couple of lines. So when we call over the phone, we not only listen to the words, but also to the tone, speed and dynamics of the voice. When we talk, we watch movements, facial expressions or any other tells to make the conversation easier.
In a videogame we do that by what's called an emote. In other words describing all the supplementary things mentioned above. This can be done several ways and it usually depends on the person, different roleplayers are used to doing this differently because they come from different backgrounds. I often try to mimic their way to make it more comfortable for them, but lately I prefer stars. You simply talk and then put the description into stars.
Oh hello there! *Kyzzi smiles, waving her hand*
putting in 'Kyzzi' is optional and again depends on the person, what you could do is:
Oh hello there! *smiles, waving her hand*
It is obvious that your character does the action. Putting in the name may be useful when writing more complex descriptions to make it understandable.
Some people use -action- instead of *action*. And recently the emote command was introduced into the game, which replaces the need for stars. You use a command to indicate you are describing an action and it makes it into an emote. This would look like:
Oh hello there!
/e smiles, waving her hand.
That way anything after the /e is made into an emote. Note that you need to send what your character is saying and what it is emoting separately. (Two lines instead of one.) This does make things more dynamic and more readable at times. It is easy to get lost in a large block of text, especially if you aren't used to the concept of emotes at first.
What if I want to say something out of character?
Usually the general idea is to put it in double brackets. That indicates it is out of character and most roleplayers will understand that.
What a terrible creature! *looks exhausted*
((oh, one second, phone.))
How different are roleplaying servers?
There will be different views on what a RP server represents, but my take on it is it is showing a preference. A lot of people (including myself) do not like to roleplay 24/7 and sometimes you just want to chat about the game, make friends that carry over to other games or share a funny thing you heard outside of the game's world.
It of course is perfectly fine to do all that even on a RP server.
What a roleplaying server means to me is that the players there are to some extent interested in roleplaying. It does not mean everyone is roleplaying 100% of the time.
That said, it may be expected that what you say in general chat is coming out of your characters mouth. However, there are no distinct rules that would make a clear line between a PvE and an RP server.
So I can do anything I want?
As in any community both online and offline, there will be certain expectations and unwritten 'ways of acting'. It is not something you can learn by reading a forum post, but more of a thing you pick up as you go along. Different guilds will have different rules, some have their guild chat in character, some have it out of character for example.
There is one general rule that should work across all servers (not only RP), but is particularly expected on an RP server and that is:
Respect other players.
Your character may not be the friendliest person around, you may be a mercenary who does not care for anything but a couple of gold pieces. This could mean you will talk to others in a different way than let's say a knight who holds honor among anything else. In both cases, you should respect the player behind the character you are talking to.
Do not push other people into situations they feel uncomfortable in, do not force other players into doing things the do not wish to do.
Most of the other 'unwritten rules' simply come out of this one, so if you respect the players around you, you are going to be fine.
Where does RP take place?
If you read half of what I've written above, you get the idea that RP may take place anywhere at any time. While that is very true, there are places that promote roleplaying more.
Guilds. Joining a roleplaying guild is probably one of the best ways to immerse yourself in a story. It will let you meet new friends easily and often the guild will have some sort of a theme to it. A backstory you can pick up and interact with, making it very simple for a less-experienced roleplayer to be a part of something big.
When looking for a guild, you might want to consider three things:
Timezone/online members - If you are the only one online when you play, there's not much point in being in such guild.
Theme - As said before, guilds may have a theme to them. Picking a guild that fits your likes will make it much more enjoyable for you. Feel like a noble knight? Join a guild with a similar theme. Or you may be sick of all the noble knights, in that case look for a guild that is sick of them too!
Friendly feel - No matter what else the guild is, you should always feel comfortable in your guild. After all, chances are your future best friends are likely to be your guildies. Make sure the guild you are looking at has a friendly feel to it.
Events. What often happens on an RP server are events of many kinds. This can be a simple party to celebrate that it is Friday, or a great tournament where you can fight warriors. Having a look at your server's forum every once in a while may be a good idea of not missing out on any fun!
RP spots. There usually will be a few places that roleplaying people gravitate towards. This may be a tavern in a local city or a shiny point of interest. When you find a place like this, chances are you will always find a person roleplaying that is happy to share their story or listen to yours.
Good news, finally my monstrous wall of text comes to an end! :)
Remember, RP is what you make it and it should be something you enjoy that makes the game more fun! There isn't a 'right way or roleplaying', but there is a right way for you!
Hope you have a great time living out your dreams!