Once again, reading the label will guide you through the proper method of handling the pesticide. It gives you general safety information meant to protect the applicator. The label will tell you how to mix the product. Some products may be pre-mixed but most need to be diluted before application. The label also explains when to apply the product.
Some pesticides require dry conditions, others do fine even if it rains afterwards.
There may be temperature restrictions for application, a warning on wind conditions, and even advice on what time of the day is best to apply so that honeybees, butterflies, and other beneficial insects are not harmed. Pets and children should be kept away during and immediately following application. It also would be wise to let your neighbor know of your pesticide application plans so they too can stay clear. Any drift could damage desirable plants in your neighbor's yard. There might be some residual pesticide that may unintentionally come out the next time you spray.