We tend to travel 6-10 months a year, so eating at home is a luxury. While I do a bit of research before we hit a spot for the first time, a surprising number of meals come from asking Google for a "good restaurant near me" - which has been remarkably successful.

My wife is very conservative (doesn't like spicy food and a long list of stuff she doesn't eat, but even so, after 5 decades of pretty heavy traveling (accelerated since I gave up my day job in 2011), with well over a dozen month-long self-drives through Africa, Asia, South America, Europe and North America (OK - in India I hired a driver and in China we used bullet trains), we have yet to suffer an upset stomach. (That's across the spectrum from Michelin star restaurants to Indian street food).

Simple rules:

1) When in doubt, don't drink the tap water, don't eat salad washed in the tap water (meaning no salad), only pealed fruit.
2) When ordering bottled water, get sparkling water (nobody refills sparkling water, but I suspect that some of the "still" water is tap water - if ordering still water, make sure you hear the crack when the lid is unscrewed indicating it's unused.
3) Don't eat "mystery meat" (chopped meat of any sort), all meat has to be in chunks and cooked well-done.
4) If ordering stew or veggies, make sure they are cooked to order - not out of a chaffing dish (germ factory if not hot enough)
5) Bread, cheese and eggs are generally safe (probably safer than in the US)

And no, other than in super-clean places like Japan, my wife generally won't eat street food, but I enjoy the variety.

All that said, we haven't eaten in a fast-food western-style restaurant for as long as I can remember.

Jeff