Grubs are typically just below the surface of your grass. They can be easily located by pulling up a portion of your turf grass. If it pulls up easily it is evidence that the root system has been fed on by grubs and the grass will likely start browning and dying shortly. Grubs may come to the surface of your lawn after heavy rain storms as they are escaping the flooding soil. 

Grubs are most common in the late summer months. They tend to prefer nutrient rich soil that is well taken care of and can easily be maneuvered through. Regularly aerated lawns are preferable to grubs as the soil is not too dense and root systems are able to travel deeper making them easier for grubs to locate.