Quick Tips For Everyone
At all times, be aware of your surroundings, your belongings, and do not let your guard down. Do not make yourself unduly vulnerable via alcohol or drugs.
Stay up to date on current events and local and national laws. Make informed decisions on where to go, or not to go. Contact law enforcement or your embassy if you feel you need assistance.
Leave ALL of your expensive valuables at home if you can. Do not wear jewelry, nice clothes, purses, etc. so as not to be a target. Do not leave backpack, computer, etc. unattended at any time.
Make friends, but be cautious. You will need and want to trust others, but use your gut. And always have someone you can check in with often and reach out to for help if needed.
Specifically for Vanlifers
Not only for personal safety, but because many roads you encounter will have TONS of potholes, random speed bumps, wildlife/farm animals, and pedestrians. Get off the road before dusk unless it's an emergency.
Install an alarm on your vehicle. It is worth the investment. It will draw attention in a good way if someone does break in either while you're away or while sleeping which may both alert you and also scare predators away.
Refer to iOverlander or other apps to find secure parking and sleeping locations. Your vehicle will be your home, protect it by not parking in vulnerable areas. When parked, hide any valuables and use a curtain to block others from seeing inside.
Follow local laws. Do not draw undue attention by causing issues or being loud or boisterous. The less "well off" you and your vehicle appear, the less attention you will draw. Aim to blend in as much as possible.
Personal Anecdote on Safety
Before we left for our vanlife adventure from Canada to Argentina in the Summer of 2018, my fiance and I were contemplating what safety features we wanted to add to our van. We heard the news about Central and South America and we wanted to be prepared for the worst. The options included an alarm, GPS tracker, video surveillance, automatic lights, pepper spray, a large knife, signs to hang on the van pretending we have a guard dog... tons of stuff.
I posted on one of the Facebook groups for Overlanders asking what other people do to secure their vans and valuables. My post was met with jeering comments and people poking fun at me. I was SHOCKED to say the least. I was actually getting made fun of for trying to be safe. I could not figure out why this was happening. While I still believe this was NOT an appropriate response by the Overlanding Community to a newbie vanlifer concerned about safety, I now understand (to a point) why people responded with such responses.
This is why: from personal experience after 2 years on the road, traveling will likely (hopefully) never be as scary or dangerous as the media or friends and family will make you think it will be. In addition, the dangerous things that do happen typically are not directed toward foreigners (for example, gang violence) save for petty theft which you can combat by doing the same things you'd do in the less fortunate areas of your own home country to be safe.
After a month and a half in Mexico, followed by a year and a half between all of Central and South America, I can tell you from experience, 99.99% of people you will meet will be wonderful, helpful, hospitable people. You will also find that we are all a lot more alike than we are different and the majority of people want what you want: health, wealth, and happiness for themselves and their loved ones.
In the end, while we brought some extra safety features in the van, we never ended up installing anything except an alarm. In addition, we never ONCE got asked for a bribe or felt truly taken advantage of. Yes, you will get quoted higher prices than locals; get used to it, and sharpen your bargaining skills. And finally, the crappier looking the van, the better...people assume you don't have money. Worked for us!