It's impossible to blend in completely in a foreign country, but there are definitely some things that you can do to fit in a little better with the locals.
Why should you bother?
Attempting to blend in a bit makes you less of a target for scammers, makes the locals around you more comfortable, and can be a sign of respect for the culture that you are visiting.
Pick your clothing carefully and do some research before you pack
Nothing can make you stand out more than wearing short denim cut-off shorts while exploring Florence or head-to-toe black in California. If you are wanting to be left alone by scam artists, touts, and pick-pockets, attempting to blend in by dressing like the locals is not a bad idea.
My suggestion is to check out street-style websites and Pinterest to see what people in the country or city you are visiting seem to be wearing before you go. When I was in Italy years ago, everyone, both men and women, were wearing huge Jackie O-style sunglasses. I got a cheap pair and suddenly people were coming up to me and asking me for directions. It’s amazing what embracing a local trend can do to help you blend in.
When in doubt, pack neutral clothing that you can easily layer with a local item you might decide pick up. Make sure to avoid logos and showing too much skin, especially if you are visiting a country that has religious or cultural restrictions to the way people dress. (See 10 Tips For Women Traveling to Morocco).
Learn some words in the local language and don't be afraid to try speaking them out loud
Learning even a few words of the local lingo shows that you are making an effort, and it will be appreciated (even if your pronunciation is terrible).
Phrase books and language apps are great, but I also suggest writing down a few words and phrases on a cheat sheet to keep in your pocket.
My go-to words are: hello, goodbye, thank you, yes, no, excuse-me/sorry, how much and numbers 1-10 (higher if you are heading to a market where you will need to barter).
Don't wave your map around
I know that a lot of you will just use a map on your phone, but if you are using a physical map try folding it into a small square so it shows only the area you are walking in and pre-plan your route so that you don’t have to look at it every block.
Nothing will label you as a tourist more than standing on a street corner with a giant, wrinkled map in your hands.
Walk with purpose
Walking around like you are lost or in such awe that you keep bumping into people will not only annoy the locals, but will also make you a target for scam artists trying to get tourists to pay for overpriced tours.
Keep your head up and, even if you are completely lost, walk like you know where you are going.
Be respectful of cultural norms
Are you visiting temples or churches? Make sure you knees and shoulders are covered.
Are you in a country that observes the rules of Ramadan? Don't eat or drink in front of locals during the day.
Make sure that you are aware of any customs, traditions, or rules that the people in the culture you are visiting follow. You are a guest in their home, be respectful of who they are and what they believe.