That's entirely personal. I weigh daily BUT I graph it, and only watch the trend; minor blips (which can be 5# or more on a daily swing) don't affect me--I watch the pattern. Some folks find that daily weighing becomes a major obsession, and they (wisely) weigh once a week or so. (for me, those daily blips showing up on a weekly basis meant I didn't 'believe' the scale).
One thing: If you notice your life is being ruled by the scale, DITCH IT, and rely on other ways to measure progess--like measuring or your clothes fitting. ALL the scale offers is ONE NUMBER: it's not god.