Performance Tuning For A Stored Procedure

I have an SP that is big, huge, 700-800 lines.

I am not an expert but I need to figure out every possible way that
I can improve the performance speed of this SP.

In the next couple of weeks I will work on preparing SQL statements
that will create the tables, insert sample record and run the SP.
I would hope people will look at my SP and give me any hints on how
I can better write the SP.

In the meantime, after looking at the SP briefly, my first observations are:

1- use SET NOCOUNT ON
2- avoid using UNION statements
3- use WITH (NOLOCK) with each SELECT statement
4- avoid using NESTED Select statements
5- use #temp tables
6- avoid renaming tables in SELECT statements, for example SELECT * FROM
tblClients C

Am i correct to consider the above 6 points as valid things in terms of
causing
performance problems?


I would appreciate any comments/help

Thank you very much