A stored procedure must contains at least three parts: 
(1) stored procedure name 
(2) parameter list 
(3) its body

Ans)

3 Parts are necessay, see the exmaple.

 here's an example to depict the fact:- 

Create Procedure usp_delete_customer 
@cust_id int

AS 

BEGIN 
delete from tbl_customer 
where cust_id = @cust_id
END 

Here:- 
(1) usp_delete_customer is the name of the stored procedure. 
(2) @cust_id int is the parameter 
(3) Inside the BEGIN and END tag is the body of the procedure