This is really not a hard shop. The biggest thing is to be absolutely sure your timings are correct and DO NOT ask for ANYTHING special, unless you have a special order, in which case you will ask for an item to be removed. This means do not ask for lemon for your tea. Do not ask for sweetener for your tea. Order sweet tea or unsweet tea and take it as it comes. Take all menu items as served and do not ask to make any changes.
In my location, these fast foods are VERY busy during the lunch period and not as busy during breakfast and dinner. If I am doing a lunch, I try to do the drive thru right at 11:45 + 2 minutes just to be safe - time differences, I don't want the receipt to say too early a time. Earlier is best for me, because if I beat the rush, I do not sit in a long line. It's also good because it makes my timings shorter, and that appears to be the most important thing to the client. Be sure you wait 5 minutes between getting your drive thru food and entering the location. When I go in, I usually do the bathroom visit before I get in line. Be sure you stay in the dining area for at least 15 minutes AFTER you get your food.
Do not correct your order. If they give you the wrong size, do not tell them. Note it in your report. If they give you a wrong item, do not correct them. Be sure you get 3 items, entree, potato, drink. That's what they want. If the entree, potato or drink is wrong, that goes in the report. You do not correct and ask for the right thing. Evaluate the 3 items you got. If you did not get one of the 3 items, ask for the one you did not get but do not say "my order is wrong" only say "I did not get my fries (or whatever)." You want them to hand you the item you did not get. You do not want them to take the bag back, look in it, and completely correct an order. That messes up their times. If you do this, it makes their times longer and they will not accept your report.
Look at your receipt. If ANYthing is wrong, be sure to say so in the report. This includes wrong date, wrong time, if it says "Take Out" instead of "Eat In," wrong entree, wrong cost, wrong amount paid (say you gave them a $10 bill and the receipt says $20 and shows $10 more change than you got - yes, this has happened to me), or if they gave you the wrong receipt. If you didn't get a receipt after you asked once, put that in the report.
Be sure you go to the right location at the right time. Be sure you remember whether the order is special order or not. Be sure you go during the right time frame. I know these sound like no-brainers, but you would be surprised how easy it is to flub one of them.
These are the major things I can think of.