Prevention is the best cure, so keeping harmful or undesirable insects at bay is the best way to make sure you never have a pest problem. The main way to do this is to keep a clean home. Insects love filth, grime, stinky smells and foodstuffs. You should also use the aforementioned plant-based system for acquiring helpful insects and keep that maintained because the key is to have more good insects than bad. If you use an exterminator, then you're likely on some kind of a quarterly maintenance plan, even if it's just for termites. For ticks and fleas, keep rodents off your property and keep the grass mowed and underbrush clear.