It is important to know what you are treating and why it needs to die. Otherwise, you run the risk of spending extra time and money to off a good bug! Remember, there are many reasons turf could decline, so make sure mowing, irrigation, and fertility are all in check. Next, make a scouting plan that includes thresholds of when to pull the treatment trigger.
Scout, scout, scout
Ideally, making time to look for the presence of pests in the landscape is a part of your landscape schedule. Take a few minutes to look through the turf, flood out a section with soapy water, or vacuum a section of grass to see who is feasting and if it could become a concern. Scouting for pests even when there are no visible problems will help you keep pest pressure down.
Ideal situations are increasingly rare, so if you do see some decline starting to occur, this is when it is vitally important to scout for pests so you know what action is to be taken. Go to areas where the damage is moving towards to get the best sample. Dead parts have already become dinner and the pests have moved on.
Try to schedule scouting that fits the goals of the landscape. High end landscapes need more time and attention scouting and preventing issues before they become visible. Basic landscapes may have a higher threshold for acceptable damage, so you may scout a little less frequently and allow slightly higher pest numbers before pulling the treatment trigger, but damage may be visible.