I spend a lot of time in major cities, even though I don't live in one. I have some rules that I follow that aren't riot-specific but might help quite a bit.

• I always have a car. If I didn't drive to my destination I always rent one.
• I never park a car with less than half a tank of gas, and I invariably fill up at 1/4 tank or sooner.
• I do not valet park any vehicle. I know a number of people who were unable to get their car back when things went wrong with the valet service.
• I always carry enough cash to get out of whatever parking garage the car is in -- I've seen people get stuck when the connection to the credit card processor was down several times. I actually carry a lot more cash than that.
• I know the destination city's roads well enough to get out several different ways, without resorting to a smartphone or GPS. When traveling to a new city, or one where I haven't been there for a while, I study maps before departing. In the cities I spend the most time in, I have detailed knowledge of streets and neighborhoods.
• At least a bottle or two of water and a few snacks are kept in the car or in my bag, even if just a one day rental.
• I've made the effort to obtain concealed carry permits valid in as many states as I reasonably can, and I carry a pistol everywhere I may legally do so. Checking a bag with a pistol is a pain when flying but I do it anyway. I've chosen to be a lifelong student of the pistol; I recognize that this is not for everyone.
• Even my minimalist TSA-safe emergency kit is way, way better than nothing, and it's always with me when traveling.

Given recent events I'm making the effort to carry more ammo on my person and I'm planning to work harder to be aware of large gatherings.