Marriott stopped issuing 713s after July 31, 2001. So I'm curious as to what award you actually have.
If it is truly a 713, you had better get busy and use the hotel award(s) or return it for credit. With the exception of some 713s that were issued in connection with the purchase of timeshares, the 713s generally expire at the end of this month.
You should have received two certificates that look similar. One is the 7-day hotel certificate. The other is a rental car discount certificate. At first glance, they look alike.
If you do in fact have two 7-day hotel certificates, I assume you will do the right thing and return the extra one....
You must make advance reservations telling them that you plan to use an award. Merely present the certificate when you check in. If you make reservations without so advising them, you will be out of luck when you check-in.
Award rooms are capacity controlled. Forget about using an award to stay at most top resorts this summer if you haven't already made reservations!