If you know you are pregnant and are further along, miscarriage
symptoms are bleeding
and cramping. However, many women will bleed in early pregnancy, even passing small clots. So again, the only way to know is diagnoses, usually through ultrasound.
If you suspect you are miscarrying, or have had a miscarriage, you should see your Dr. or if you are bleeding more then a maxi pad an hour, you need to seek emergency medical treatment.