Don't wear white leather tennis shoes. Nothing screams AMERICAN TOURIST like white leather tennis shoes. Buy the cheapest watch you can and skip all the jewelry. Pack light. Understand local customs and manners. Pointing the bottoms of your feet toward other people in many countries is very rude. This includes resting your lower leg across your opposite thigh while you sit, which is very common in the US,etc.
If you learn absolutely nothing else in the local language, learn a friendly greeting, thank you, and "sorry" for those times you inevitably goof something up.
We use steri-pens when we travel. Very nice device...
angela