Nitrite comes from Ammonia, so the steps you would take to keep your Ammonia under control are also valid for Nitrite.
Cycling your aquarium: again, this is a must. Those good bacteria created during the cycling will consume your aquarium’s Nitrite helping you to keep it under control. Read more here about cycling your aquarium using different methods and which is the best and fastest way.
Do not overfeed your fish.
Remove dead plants, fish, snails, or anything that could decompose in your water.
Keep your aquarium clean, replace and clean your filter media frequently.
Keep up with your water changes routine.