When in doubt, go for the event with food.

 Assuming you have a number of events to pick from in your area, though this may not be the case when starting out, one big deciding factor for me can be food. Let me explain why. 

1) Whenever working at an event, it typically takes an hour or two for setup, then there is the event that could last just a couple of hours to an entire day (sometimes multiple days), and then you have to break down everything. It is best to have food with you. Whenever I can, I pack a cooler with drinks and food. Sometimes it is just a sandwich and snacks, but if there is no food available to purchase, I pack even more food than that. You know why? It burns a lot of calories setting things up and breaking things down. Sometimes it is a long walk toting heavy items getting to the event itself. Even if you think you've packed enough, it is great to have another food option available. No one likes to shop from a hangry business owner.

2) Food brings out more people. Sometimes in my area, there are several vendor events in one town. And then even more events in other neighboring areas. I've found that people are more attracted to the events that offer some type of food. If an event is promoting plenty of food trucks at an event, it makes it even more appealing to most attendants. Also, food trucks typically suggest it is a bigger event and that brings a crowd, too. The more people, the more potential customers for you. The more food that is offered, the longer people will stick around the event and that is more chances to sell to them.