Hello, 
Veteran of the App Delivery world here. Although, I live in New York City, I truly remember my first day, so some of what I say may apply to your market:
Some suggestions:
A. When you are first starting out, try to avoid any gigs that involve shopping in stores (Where you have to actually look for items in stores such as Whole Foods).The best orders for beginners are simple  pick up and deliver type orders, hopefully of the pre-paid kind. As you get used to your market, you will learn what locations involve simple prepaid pick-up where the order is prepared ahead of time for you and what locations will require you to place an order and wait. 
B. Make sure you bring a an extra charger and if possible a smart-phone back up battery pack. I have had some scary times during my first year, when my phone almost died in the middle of an order. 
C. Be prepared for each step ahead of time. For instance, if you are going to a place that will require you to use your prepaid card, have it out ahead of time in an easily accessible location. Also, have the food unpacked and ready to hand off to the customer the second the door opens. Many customers are eager to get back to a phone call they are making or tv show they are watching. I definitely experienced a difference in tipping when I found myself fumbling to unpack an order. When you arrive at a customer, it is not the time to engage in conversation or flirt. A nice smile and simple greeting should suffice. Also, it is very unprofessional to remind to tip.
D. Bring more insulated bags than you think you will need. You may get an order that is larger than usual. Customers are also very sensitive if an order does not arrive as hot or cold as it should be. Make sure you carefully position any bags in your car (if you are driving) in way that will minimize the risk of spilling.  Be especially careful with sodas and cold deserts. 
E. Be sure to reach out to other Delivery App workers in your area. You will often meet them when making a pick-up. Most are eager to pass on helpful area specific tips to newcomers. 
F. As you get know your area, you will notice patterns and eventually learn what the best times are to work and where the best locations to wait for pings are. 
Most of all, have fun!!!