Adam Szymkowicz has posted 300 interviews with playwrights, but this may be the best one yet: Anna Moench. Her advice:
Get a news site to email you all the articles about some random country
every day for a year. Become an armchair expert on something. It will
probably start to show in your writing. Or even better, you may end up
at some horrible party where some insufferable person is talking out of
their ass about North Korea or whatever and you can be like "SHAZAM! I
know everything there is to know about North Korea, fool!" That has
never happened to me, but I haven't given up hope.
