There are gnats, that usually come from moist potting soil, and there are "fruit flies", actually vinegar flies, that appear when overripe fruit is left out, and then there are grain moths that appear when flour, cereal, and other grain products are not properly stored.
Of course the best way to combat these is to prevent their appearance at all by properly storing your fruit and grain products and allowing the pots to dry between waterings. If you do get them blue and yellow sticky traps help control them as well as some few other things such as diamoataceous earth (food grade), in the pots and grain products and insecticidal soap sprays. But the vacuum works well too.