Orthodox clergy have beards and often wear black; Catholic clergy are clean shaven and often wear white.
Orthodox iconography is more notional with less realism than Catholic iconography.
Orthodox liturgy is sung without instruments.
Orthodox communion has pieces of bread versus Catholic wafers.
The Byzantine Catholic Church has all of the below except for the beard as well.
The bread issue—leaven vs unleaven was one of the bones of contention contributing to the schism between the Eastern(Orthodox) and Western Church in 1054.