A lot of people who run use headphones and something I have noticed is that most of them keep their buds in both ears. Can I make a suggestion?
Don't do this.
If you must run with music, only wear one ear bud. Let the other get tucked in your shirt, or hang freely, but you are missing out on a lot with both those ear buds in. The runner coming around you, the bike you almost cut off, the car slowing down, the dog who got loose from his yard... the list goes on. Some of these things can be no big deal, or a simply sorry will suffice. But some of these things can be a danger you want to be aware of.
I appreciate wanting the music to distract your mind from the running, or to just enjoy the music, but leave one ear free to pay attention to your surroundings. You don't want to be that distracted.