1) Best way to avoid underwatering and overwatering situations for houseplants is to provide the sufficient amount of water that means only provide the required amount of water until the soil becomes wet not soggy.(avoid standing water in the pot for longer periods).
2) Major Steps to be followed to get rid of pest infection:
a) Isolate the plant: If the indoor plant is infected with pests, it's important to stop the spread — especially if it's in a room with other plants. Make sure you isolate the plant (such as placing it outdoors or in another room) while also monitoring your surrounding plants closely for signs of pests in around three to four weeks.
b) Deep clean: Thoroughly clean the plant, either use a little soapy water or a damp cloth to wipe away the pests and the area where the plant was sitting using soapy water. For extra precaution, you can also sterilise the area by rubbing it with alcohol. Just be careful not to touch your eyes whilst doing so
c) Use Neem Oil: Mix neem oil, which is an organic insecticide. with a mild dish detergent and water. Spray neem oil on the plants in the morning or evening when beneficial insects are less active. The natural substance in neem oil affects an insect's feeding abilities, growth, and development, plus acts as a repellent. According to the Environmental Protection Agency, neem oil is safe to use on vegetables and other edible plants, as well as ornamentals.Repeat every seven days until the infestation is gone.