Don't try to conform too much to the racial stereotypes. Don't overdo them if you choose to use them. They are good as a basis but a lot of players tend to think "I want to play an unique character of X faction so i'll do the exact contrary of its clichés !", which as you can guess, completely destroys cultural specificity.
The best way imo is either to think in racial stereotypes if you look for something rather safe, but the trick is to do something else with it. The stereotype has to be the core of the character, but not necessarily his personality. Pieter may be exactly what we expect of a brainwashed tube child prole bathed in Caldari fascist propaganda at first, but you just have to watch the character itself and it doesnt sound like it at all anymore. Well, at least, I think so.
Or either, my favorite way is to put a great emphasis on cultural relativism. Look how the Caldari culture is and what makes it that way, and try to put yourself in the shoes of the Caldari and not a RL westerner. Or the other way, in the shoes of the westerner, how alien the Caldari culture is to you and try to explain why. If you can understand why your character due to his upbringing thinks his faction is the natural way to go, then you nailed it. It is not necessarily good to think in altruistic ways like a lot of players do. I don't think that other empires than the gallente aren't altruistic and are like obscurantist backward reactionaries of the middle ages - actually I believe they are altruistic in their own way. What may look altruistic to a gallente will be different to a caldari or an amarr or a minmatar. What may look honourable will vary, etc etc. What will look honourable for a minmatar, saving his kin and tribe, will sound completely dishonourable and selfish to amarrians that consider that sacrifying oneself for the mistake of one's kin is honourable, or will sound completely dishonourable to a gallente that consider the one self above everything, and everyone equal, where a minmatar will just not care at all for other tribes and kins. It's just like changing the lens you look through.
More precisely, RP needs more cultural relativism. If I remember well, you did not that bad regarding that particular point on the IGS in the past...
Then, for a caldari, the mega (or lack of) defines the individual. Which is the mega to which the character belongs ? Has he seen other megas (rather rare) ? Is he disassociated ? And then, what position ? Prole/workforce ? Security ? Administration ? Director ? As much as the State can praise meritocracy, it is still all in the eye of the beholder. Who defines merit and what is worth ? How does a director live compared to a forklift driver ?
And not the less important, the character himself. What is his personality, not only in relation to his background, but also, how does it confronts his Caldari upbringing and social position ? The personality is important so that it offers an interactive way to create story material when confronted to the cultural position of a character and defines how he will react to it.
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For the ni-kunni, there are a lot of angles that can be exploited. How they were reclaimed (Oooooh, look, water, me thirsty !), their current position in the Amarr celestial order and ladder, their "exotic" side... And then the Amarr social structure itself.
- Noble ? Commoner or ex slave ? Slave ?
- Part of the low clergy (priests, etc) ? Part of the high born clergy (Holder, noble, theologian) ?
- Part of the imperial administration under the direct imperial authority (Navy, Civic Court, etc) ? Or working for a liege lord (Holder demesne) ?