1) Make sure that the character(s) you're writing about has a good, solid, believable REASON to angst. Also, the type of angst should match what the reason is and how deep it goes - whether it's a breakup, a popular cheerleader angsting over how nobody really "knows" her, a kid in an abusive situation, a drug addict, a homeless man, a young woman who's fiance/best friend is dying, a superhero with the weight of the world on his shoulders, etc.
2) Draw inspiration from your own personal "angsty" experiences and/or characters and stories that you understand and relate to. For example, a character I deeply empathize with is Edward Elric from
Fullmetal Alchemist. While our personalities and backstories couldn't be more different, we share a lot struggles and inner demons; in fact, watching him deal with his pain has helped me come to terms with my own, a little. And that enables me to write more powerfully and authentically about those things. I don't have to fake it, because I already
know it. (
link) Just remember - the more of your own life and heart you pour into the words, the more it will ring true with your readers and bring them to the point of reaching for a kleenex box. (And plus, it's a great substitute for therapy.) =P
3) DON'T OVERWRITE OR SPELL IT OUT. In other words, don't write anything like, "The depressed emo kid with no friends was drowning in a suffocating, cold, deep, dark ocean of darkness and despair and agony and he knew death was his only hope so he cut his wrists and DIED and it was SO TRAGIC!!! ARE YOU CRYING YET??" The readers aren't stupid OR heartless, so don't treat them as if they are. They don't want to be spoon-fed emotion; they want to discover it and feel it for themselves. That's what makes it powerful.
4) Make sure there's a method to the madness. Don't randomly dive into it. Going hand-in-hand with everything I've already said, angst doesn't just magically happen or pop out of nowhere; something has to
make it happen, to build it up, to trigger it. And the character must react and deal with it accordingly. So make sure that the angst and soul-searching flows well, has a purpose, stays cohesive and moves the plot and/or character growth forward in some way. What's the point of angst if you're not going to do anything with it? Or
about it?
5) This is a principle that I hold very dear:
happy endings are every bit as powerful and meaningful as bitter beginnings. Sometimes you just need to fight for them. Nobody likes staying depressed forever! By all means, angst away to your heart's content...but having the character overcome the pain and earn a hopeful ending will inspire your readers and give your whole story twice as much power.
