Make sure you look at the items before you judge the order - a 30 item order might be much faster (it's all baby food and soup) than a 13 item order (its all behind the counter items and commonly out of stock items). Try to stick to a few stores that seem busy to learn the layouts like the back of your hand. Produce is much easier to shop for before you hit "start shopping" at most stores, when you view the entire order on the screen before you actually start you get a much easier to read layout. Don't waste your own time when you don't have to - it might be better for the customer if you're willing to wait five minutes for a response every time to get the perfect substitute but at the end of the day it won't help your rating enough in the long run to be worth it. If you start to feel like an order is going to take way longer than you thought or that the customer might be a headache, just cancel.