So, instead of writing a list of "do's" when it comes to writing a strong female character, I've written a list of "don'ts" that I think could be more helpful.
Things that DON'T make a female character strong
1. Giving her a strong background story - then leaving it as background. Giving your female character a deep and well written background showing a history of strength and independence is great, but it's meaningless if you only reference her strengths in the past and don't show her being strong in the present. I don't care if your character was raised by wolves or single handedly defeated an entire army of marauding beasts; if she's acting helpless in the present your reader won't believe she's strong. I've heard this called the "Trinity Syndrome", where, like Trinity in the Matrix a female character will have an awesome introductory scene; they save the male main character, they kick but, then once the hero is on his feet their role in the story is to be nothing more than the male hero's love interest. Even Bella from Twilight suffers from this. Many might just consider Bella a weak character all around, but she has a moment where she's talking about how she used to look after her "hair-brained mother" and shows strength in supporting her mother's decision to follow her new boyfriend to Florida, but then for the rest of the book Bella becomes the damsel in distress, constantly being saved by Edward.
2. Not giving her weaknesses - Yes, you want to write a strong female character, but you want her to be human, not a robot. Writing a strong female character is not the same as writing a "Mary Sue". She should have faults, weaknesses, problems. She should make mistakes, and she doesn't always have to win. It's how she handles the issues in her life, and how she grows from them, that will show her strength. Any character, female or male, who is always strong and never loses, is boring. Nancy Drew may be a strong, smart woman, but being a goody-two-shoes who excels at everything she does makes her boring. I also think Katsa from "Graceling" suffers from this problematic strong female character trope, she's strong - stronger than Po, her love interest, and manages to beat the unbeatable evil king. Even the few weaknesses she does have, like being incredibly stubborn, manage to benefit her in some way. Read more on my thoughts of "Graceling" here.
3. Not giving her anything to do - You can create a great female character who is strong and independent, but she has no purpose in your story if she doesn't somehow advance your plot . Don't throw in a strong female character just to have one, you have to give her something to do. This is like letting Wonder Woman join the Justice League and making her the secretary. Or, remember the movie version of "League of Extraordinary Gentlemen"? Lone female character Mina Harker, is an awesome reinterpretation of Bram Stoker's weak, victim Mina, however in the League book she was the leader of the gentlemen, but in the movie she felt like she'd been thrown in just to say "hey, we've got a girl!".
4. Letting her overshadow the lead - If your strong female character is your main character then no worries, but if she's a supporting character, don't forget that she's a supporting character. Supporting characters should help your main character resolve the plot's main problem, they shouldn't completely steal the spotlight. Rita Vrataski from "Edge of Tomorrow" is a great example of a strong female character who manages not to steal the spotlight. Also, Julie from Isaac Marion's "Warm Bodies" was an awesome character who moved the plot along and was a great counterpart to the lead R, but never stole the show herself. She worked with R to solve the book's problem.
5. Making her physically strong - and that's all she is. Having a female lead who's got muscles, or superpowers, or can make her way in a man's work is all well and good, unless that's all she is. A true strong female character does not have superficial strength. A woman who's tough as nails and can fight her way out of anything may be strong in some ways, but she's boring and paper-thin. Having a character with a deep backstory who's important to the plot is a stronger character than one who's got big muscles, but thinly written. Don't write a Lara Croft who comes off like a male main character with boobs and no real reason to explain why she doesn't feel like a real woman; write a Katniss Everdeen who's physical strength and skill are explained with backstory and any moments she lacks emotion are seen as a defense mechanism instead of her being a robot. Or, write a Hermione Granger who's strength is intellectual and rooted in her fierce loyalty to her friends.
All and all a strong female character is less about their strength and more about how they deal with their struggles.
Maybe we should all stop focusing on writing a strong females and instead focus on writing a real female character who has both strengths and weaknesses. I don't want to see anymore characters who are completely weak like Bella Swan or Nora Grey from "Hush Hush", but I don't want to see characters that completely lack weakness like Katsa either. Lets focus on writing female characters who are important to and contribute to the story, and handle their problems in a believable way.
