To some extent, by dressing like the natives, including wearing of the shoes that they wear, you can blend in somewhat. Behavior, such as looking serious, walking fast and with purpose, helps. On the other hand, you may want to gawk at Big Ben, Eiffel Tower, or Sugarloaf.

I often carry a briefcase instead of a backpack. I've been asked by tourists for directions, one time even in French. The couple made a big assumption that I could understand it as the country was not a French speaking country. On the other hand, maybe they had no choice but to speak French.

Sometimes, you can't avoid being spotted as a tourist. While in eastern Morocco, I stuck out like a sore thumb. Some people did not know I was American, though.