Regular water changes will keep nitrates down, but they won't reduce them to zero. Essentially, you dilute the nitrates with each water change, but you never export all of them. Still, this coupled with keeping feeding to a minimum is your first line of defense.
I've had great luck growing chaetomorpha (a seaweed) in my sump. That will export nitrates very effectively. If you don't have a sump, you can easily add some kind of small hang-on refugium to accomplish the same thing.
Another common trick is the use of cleaner clams, which you can buy on this site or even at the grocery store. I have not had great luck with this. They work well for a while, but you never know when they might just die...and you can't get them out of your tank when that happens becuase they always bury themselves. So maybe they suck some nitrates for a while, but then they pollute the tank eventually.
Good luck!