Unless the level gets horribly high, once a day is enough. If the level does get horribly high you may need to do more than one water change a day and testing twice a day.
Feeding the fish less and once every two or three days also helps. Less food means the fish excrete less ammonia so there's less ammonia to be turned into nitrite. Once nitrite stays at zero, feeding can be increased slowly - though most fishkeepers do overfeed their fish. They need a lot less food than you'd think as, unlike us, they don't use food to keep warm. They get their warmth from the water.