To remove buggage from the plate and the rest of the front end, rinse thoroughly and spray on a diluted mix of an all purpose cleaner, let it work for 30 secs then wash with a soapy mitt or sponge. Rinse again and repeat if necessary.
A good coat of wax on the plate will help minimize bug residue buildup. You're prolly better off removing the plate from the car and cleaning it by hand separately.
If the plate is attached to a plastic mount that is bolted onto the nose of your car, clean that also and apply a thin coat of protectant or dressing to the mount. Like wax, it'll keep bugs from sticking to it.