Keep your friends and family posted of your whereabouts.
Research the place you’ll be going
Join a tour group
Don’t ride in cabs that aren’t registered with the city
Avoid wearing jewelry
Don’t get too drunk
Don’t put your money in one bag. Divide them in case you get robbed.
If walking alone at night, walk behind a group of people
Avoid dark alleys or non-tourists areas
Be confident and don’t look lost even if you are