Duplicate records in my table

Question

how to find a Duplicate records in my table

anyone please help me

iam tried iam send query please check it this is right or wrong

give me duplicate records from the following tables

Select * from DimMember - firstname,lastname,dob

my query is 

select firstname,lastname,dob from dimmember

group by firstname,lastname,dob 

this is right if wrong please send me query