When I travel to other cities, I always like to eat where the locals eat. One of my favorite sites to read reviews is Yelp.com. I always look for restaurants that have a lot of reviews because there's more accuracy in the review. If a restaurant only has a few reviews, I tend to be a bit wary.

I don't travel that extensively, certainly not abroad, but a great place to check restaurant reviews online here in the US is foodbuzz.com. The have members from all across the US doing reviews for all types of restaurants in most cities.