1) When taking taxis from an airport to your hotel, travel in the more expensive airport taxis and ensure that the drivers have official identification. Never take a taxi waiting outside the airport grounds.

I know this sounds extreme, but it is by far better to be safe then sorry. 

2) When traveling from your hotel to the airport, go with a taxi recommended by the hotel. 

Again, taxi’s can be very dangerous. I can’t express that enough.

3) Try not to arrive in a new city or town late at night.

This can just go wrong in a number of ways. It is much easier getting checked in during the day time and security at night in certain areas is just horrendous. 

4) Travel in a group if possible.

Since when is traveling in numbers not a good idea? 

5) Learn the basics in the local language before you arrive. Don't expect that people will speak English.

English is becoming more widely spoken these days, but you want to be sure. You should always check on these things before your arrival. 

6) Keep your valuables hidden.

A money belt is great if it is an option that you willing to look into. There are many different styles of money belt. One of the most popular is an “over the shoulder” style wallet on a strap that you were underneath your top. This makes it very difficult for a thief to make off with your valuables. 

7) Avoid going on your own to remote areas/ruins where tourist would be expected to go. Seek local advice or take a guide. 

8) Read the guide books and talk with other tourists to find out which areas are best avoided. 

9) When leaving discos late at night take a taxi home no matter how close your hostel is. Outside most discos you'll find a street vendor selling cigarettes. Usually these people know all the taxi drivers and can recommend a safe one. 

10) When arriving in a new town, keep to your original plan and stay in the hostel that you have decided on. Don't let the taxi driver persuade you that your hostel is fully booked and that he knows a cheaper and better one. He'll be working on commission and the hostel probably won't be in a safe part of town. 

11) Even better, when arriving lane/train in a new city, try to reserve your hotel in advance, preferably with a hotel that has an airport/station collection service. 

12) Don't wear expensive looking jewelry. 

13) On public transport have your day pack close to you at all times, preferably with the straps around your legs or padlocked to the luggage rack. On buses your backpack will normally go outside, either on top of the roof or in the external luggage compartments. On long distance buses ask for a receipt for your bags. On short rides just keep a careful eye out each time the bus stops to off-load bags. In the event of having your bags stolen, stay with the bus - you will probably require a declaration from the bus company accepting responsibility for the loss in order to claim any money from your insurance company. 

14) Leave your valuables in your hotel safe when making day trips or longer tours. Obtain a receipt not just for your money belt/wallet etc. but for its contents, with each item listed. 

15) If you have to leave your passport and credits cards together, place the credit card in a sealed envelope and sign your name across the flap. This way when you return you will know that nothing has been tampered with. 

16) If planning on going to market areas, crowded streets, fiestas etc. don't go with all your valuables. Leave them in the hotel. If you’re planning on buying something expensive keep your money safely in a money belt. Try to be discreet when opening it! To protect small change in your pockets you can stuff a handkerchief in after. 

17) If the pavements are really crowded, especially in market areas, walk in the road. 

18) If you suspect someone is following you, stop and stare them in the eye until they go. If you really get a bad feeling about a place, go with your first instincts and leave. Bag slashing is rare nowadays but for added safety you can wear your day pack on your chest. 

19) If it's on your back try to walk without stopping. If you need to stop, sway your pack gently from side to side so that you can feel if anyone is tampering with it. 

20) When putting your bag down on the floor, to take a photo or just to sit in a café, remember to put your foot through the strap. Not only will it be impossible to snatch, you also won't forget it! This is the most common type of theft - tourists forgetting bags in cafes and on returning to ask if anyone has seen it, you've guessed it, it's gone.