Use of like operator with sorting

Hi,

I have a stored procedure that selects staff details like firstname, familyname, email, address etc . The stored procedure accepts 1 parameter  

1) SearchString

which can be null

I need to write a stored procedure to send all students if SearchString is not provided and if SearchString is provided then it should see if either firstname contais SearchString or familyname contains SearchString  or email contains SearchString   or address contains SearchString  and should return those values. I do not want to use if blocks and write it . Is there any other way