Foreshadowing is a lot easier to handle in books or movies, since everything is scripted from the beginning -- but you can still act on some of the same principles. When something comes up that trips a particularly sensitive area for your character, that's when she should speak up.
Let's say, just for example, that you're playing a captain in Star Trek Online who felt particularly bad about an incident during which she handled a first contact with diplomacy, only to later learn that the species she was making contact with had been raiding and destroying Federation outposts in the region. If she comes across another heretofore unknown species presenting themselves in a friendly tone and everyone wants to talk with them, she should be howling to power up weapons and get ready for a trap -- even beyond the point of the naturally paranoid members of the group.
Now, the golden rule in these sorts of situations is to not hold up the actual game with one character's issues if not absolutely necessary. But you should play up the idea that your character has certain trigger spots, things that bother the living hell out of her for reasons she never properly explains. She should go along with everyone else after a few moments, but her objections don't go away. And on the same note...
Clearly, telling everyone what happened produces issues. Oddly, doing the exact opposite not only avoids those issues but has some magnificently positive effects.
Let's continue using the above example. If someone asks why your captain is so insistent that the situation is a trap, your first instinct is to explain what happened. The problem is this immediately removes the mystique from the situation. Instead of becoming a long-running character trait that hasn't been fully explained, your captain's paranoia becomes far more easily ignorable from that point forward.
Human beings do not like to admit when we screw up, and for all the nonhuman species available in MMOs, most of them generally have essentially human thought patterns. So let your characters act more human. When pressed, your character offers some sort of an excuse or (depending on personality) just deflects the question outright. It's not until the issue comes up again that someone starts noticing that she behaves with the same paranoia and zeal toward unknown species.
Fact is, when we screw up our first instinct is usually to whine. Our second, however, is to ensure that whatever went wrong is never going to happen ever again -- and to do that, we need to make sure that we're not walking into the same situation. Ideally, your character's regrets and history should be walked backward from the character's current personality and habits.
Stepping away from the prior example, I'm going to use my Blood Elf Paladin from World of Warcraft. She survived the Scourge attack mostly due to her parents -- she'd spent most of her life partying and drinking and hadn't developed the skills to even try to help defend her city. It was a big issue with her, something she hated to discuss but that inspired her to become a paladin and try to defend others.
But it was about more than just her class choices. She refused to let those she cared about get too close to danger, insisting on going herself on the premise that she was more capable or durable. (You can imagine there were issues with being overprotective.) At times, she was so consumed by a need to keep others safe that she moved into hyper-aggression, reasoning that destroying potential threats was well worth any wanton damage inflicted in the process. And she was obsessed with training, with being useful, to make up for the one time when she wished she could have been useful and wasn't.
Look for hooks
This is a quick point, but a significant one. There's a difference between deflecting just enough attention so that people are curious and deflecting so much attention that no one cares. Spend too much time with your character being all evasive, and ultimately no one will wind up paying attention to your character's outbursts any longer, because she's just apparently socially retarded.
For the first couple of times, if someone asks, deflect. After that, if someone asks "why does X get you so worked up?" You should probably answer, at least in brief. That doesn't mean you have to give away every detail -- to go back to the Star Trek Online example, you could mention that she should have been more cautious but not mention that she was hunting raiders in the area in the first place -- but you shouldn't reward continued questions about your backstory with denial. Eventually, people will stop asking if they never get an answer.
The last isn't something you can do to make your character's backstory more visible... but it makes others more likely to care, because if someone's doing all of these things, he's fishing for interest.
Not only is that a clear path to make at least one other player remember that you care about the backstories of others, it's just the cooperative thing to do. Pay attention! It makes everyone happier.
As always, let me know what you think in the comments or via mail to firstname.lastname@example.org. Next week it's time to take a look at interactions between archetypes, and after that I think we've got one more archetype left before we're done with the overarching meta-feature.
Every Friday, Eliot Lefebvre fills a column up with excellent advice on investing money, writing award-winning novels, and being elected to public office. Then he removes all of that, and you're left with Storyboard, which focuses on roleplaying in MMOs. It won't help you get elected, but it will help you pretend you did.