Smart move is to let your game speak. If someone's talking trash to you and you're thinking about what to say to get into their head... That means they're already in your head. Let your game speak. I always thought staredowns were pretty stupid and like a fake tough guy act. It's not intimidating anyone unless you're a little kid.
Trash talking can be pretty fun, but I would keep it out of an organized game because of technical fouls and looking bad in front of your coach. When I do trash talk though, I try to keep it tasteful and about the game. Nothing racial, personal, etc. because that can wind up being dangerous if you're playing the wrong people.
I'm a nerdy looking Asian kid and I played a lot of basketball in ghetto San Bernardino. I got trash talked a lot, including people calling me Noodle boy/new Asian jokes every game (pretty funny actually), and I always got picked last/not picked because of how I look. That's when I learned how to let my game speak. I'd play there everyday, and after a few weeks I started gaining respect from others without saying a word. I heard them complimenting my crossover, my hops, my speed, my defense - all of the things I've worked on. I started getting picked more often because teams wanted my defense. I randomly ran into one of the best regular players one day near my house, and he gave me a lot of props, stuff he never said in the games. Let your game speak.