For a smoother sauce, sift your flour before adding it to eliminate any clumps.Cook the flour-butter mixture (roux) until it's a light golden color to remove the raw flour taste without over-browning.Heat the milk before adding it to the roux to integrate more easily and reduce the chances of lump formation.Taste and season in stages; starting with less salt and gradually adding more allows you to control the overall flavor and prevent over-seasoning.If your sauce is too thick, thin it out by adding milk a tablespoon at a time until the desired consistency is achieved. Conversely, if it's too thin, cook longer to reduce or add a bit more flour to thicken.