Make sure the wick has the correct length and fits properly inside the burner. The wick should not extend too far above the burner, as this will create an oversized flame, leading to soot buildup and overheating. In most cases, about 1 mm or max 2 mm above the burner is enough for a clean, steady burn.
Keep the wick clean and free of charred residue. A trimmed, clean wick ensures an even flame and prevents smoking.
Keep in mind that the flame height of different types of oil lamps may rise during the first 10 minutes of use. Stay near the lamp during this initial warm-up period.