Maybe something like this? 

CREATE PROCEDURE spDoSearch 
@FirstName varchar(25) = null, 
@LastName varchar(25) = null, 
@Title varchar(25) = null
AS BEGIN  
SELECT ID, FirstName, LastName, Title  FROM tblUsers  
WHERE   (@FirstName IS NULL OR FirstName = @FirstName)
AND   (@LastNameName IS NULL OR LastName = @LastName)
AND   (@Title IS NULL OR Title = @Title)END

Best Wishes,
thank you in advanve for help and support,
Jacek