More about backstory--
We know we need it, so make it work. Part of the problem is that "layered-on" backstory (that which is meant to make the reader feel sorry for the character or understand some motivation) often ends up just being contrived-- the rivets are showing, and the reader can feel the extraneousness of it. "Right, right, she was orphaned and we're supposed to feel sorry for her. Got it."
One way to counteract this is to make the backstory congruent with something in the present time. This is probably pretty basic, but I'm going to say it anyway! The purpose of backstory is to show how the past affects this character in the present. That is, a child who was orphaned (parents died) is likely to have abandonment issues as she grows up, and this might mean that she is reluctant to fully give her heart to a lover-- she knows how cruel fate can be, ripping him from her just as fate ripped her parents from her.
But notice that her abandonment issues will be different from those experienced by a man whose parents -deserted- him in childhood. That boy-grown-man is likely to distrust PEOPLE, not FATE. So he's not worried that this loving person will be ripped from him; he assumes that this person doesn't really love him and will leave. (And maybe that there's something wrong with him that makes people leave him.)
This makes the character and backstory work together for coherence. But the coherence requires us as writers taking the backstory we invent seriously, and imagining what it would REALLY cause in this particular person. That is, stop thinking of it as "backstory" and start thinking of it as "her/his past".
Other examples? Hmm. In romance, often the heroine is recently divorced, and it seems to me the cause of divorce is as important as the fact of divorce. Too often, I think, the writer misses an opportunity here, presenting the cause as something generic (usually the husband cheats on her, often with someone close to her-- a best friend, her sister?). That double-betrayal OUGHT to cause a particular kind of trust issue, but usually the character is shown to end up with a sort of generalized aversion to men. (Actually, many real women in that circumstance would end up far more wary of getting close to another woman, as the betrayal by the friend/sister might seem the greater.) Anyway, I say this is a missed opportunity, because in settling for the generic backstory (and yes, take it from me, it's pretty generic), the author loses the chance for coherence, the sort of connectivity of past and present that make this character seem real to the reader.
For example, hmm. Let's say that you want your heroine to feel ambivalent about her brilliance or talent. This is especially true in the past. A woman with great artistic talent or scientific brilliance in, well, just about anytime before 1980 (and even now, alas) might worry that this would make a man feel inadequate, or spotlight her as "weird" in society. So if you set it up that she is divorced, don't go with a generic "can't trust men" sort of divorce-backstory. Make it particular to this story and this character. The husband couldn't deal with her greater talent or success or intelligence. She won some big prize or grant, and that was when he chose to leave, because he couldn't take her greater ability. That would make "success" a real danger to her, as it led directly to her loss of her husband.
But also notice that it would make her suspect that even someone who loves her is unlikely to accept her as she truly is (brilliant or artistic or obsessed with something), and in fact that what she might consider the best aspect of her is precisely what would scare men off.
Much more coherent than just a generic "can't trust men" backstory connection, because here, it's not just that she can't trust men-- she can't trust her self, her true self. And of course it sets up for the eventual resolution, that the one man who can accept and love her talent and brilliance is the hero. It also, notice, sets up events where the talent and brilliance come into play in the plot, which makes her active (using her skills) but also creates conflict (if she has learned to hide these skills and now has to show them, not knowing what the hero's reaction will be, but expecting the worst, because of the divorce-cause already established in backstory).
Other examples? We should just keep in mind: Backstory might be just a writing element to us, but to our characters, it's their PAST.