My recommendations regarding the Security issue :

You can read information about my trips on my sites about : Vietnam, Thailand, Barcelona, Tel-Aviv and Jerusalem.
Safety depends a lot on your destination; there is a difference between traveling to South America or to Europe. Here are some general travel precautions :

Thefts

1. The Pickpockets – They are operating in all countries and especially where there are tourists. As a tourist you are more vulnerable to pickpockets because you are in a new environment and disoriented. As you arrive to a new place, there is new data that your brain needs to process and it is difficult for you to know what is normal around you and what not and pickpockets will take advantage of it. Be aware of the situations and places where pickpockets may operate and try to be more cautious. Lines for tourist attractions, malls and public transport are potential places for pickpockets. If you get a strong push by someone, like someone falling in the transports, get out of your initial surprise and check your wallet. Don’t leave your bag on the floor when you sit to eat in a crowded mall or a train station, watch your belongings all the time.
2. I like to put my wallet in the rear pocket of my Jeans, but that’s also a vulnerable location (Indeed, a thief did try to steal my wallet from my rear pocket while I was getting on a bus). These days, I divide the content of my wallet in 2 parts. The most important items, like credit cards, I put them in a main wallet and I carry the wallet in a front pocket of my Jeans. I put items that I can afford to loose like coins and the transport pass, in the rear pocket. It is safer this way and also my wallet is not huge anymore.
3. Leave your valuables at the hotel – There should be a safe box in your room or at the reception.  Don’t carry a lot of cash on you if you are not in transit.
4. Use an undercover money belt – The ones that are attached to your belt and are hidden under your clothes.
5. Don’t show off with expensive items like watches and jewelery. Match your dressing to the environment.
6. If you are staying in cheap hotels or dormitories, choose one that looks secure with video monitoring and safe boxes to guard valuables.
7. Change money in legal places. Check for fake notes. Check your change.
8. Make photocopies of your passport and other important documents. You can take them in photo with your smartphone.

Health

Travel Insurance (Health Insurance)

Travel insurance is very important. It guarantees medical assistance in case of accident or medical problem. See this page about the travel insurance

1. Vaccines – Check if you need special vaccines to your destination, especially if you are visiting developing countries. Ask your doctor about it, he should be updated with the latest recommendations. See also this site.
2. Mosquitoes – If you travel to developing countries, protect yourself from mosquitoes because they can transfer dangerous diseases. Use a net and sprays.
3. Food and drinks – In developing countries, you should take special care of where you eat, it should be clean places.
4. Wash your hands frequently and keep high hygiene standards.
5. Sun  – protect yourself from the sun (sunscreen and hat) and drink a lot.
6. Antibiotics – If you intend to do treks in mountains in developing countries, take with you antibiotics and first aid medicine.
7. Safe Sex – Use condoms.

General

1. Avoid being drunk in situations when you need to be alert. When you are drunk, you are vulnerable to many kinds of physical attacks and tricks. In Colombia, there have been many cases of drunk tourists kidnapped while taking a taxi and all their money stolen.
2. Be careful of persons putting you drugs into your drink when you are in clubs and discos.
3. Avoid messing with the local law, in some countries being in prison is horrible, in some countries there is a death penalty for smuggling drugs. Avoid unnecessary fights, be respectful to the local religion and stay out of politics.
4. Be careful with stranger approaching you. It doesn’t mean that you don’t have to make friends but just remember that there are people who approach tourists with the sole intention of getting money somehow, so judge by yourself the situation.
5. Women are more vulnerable to attacks, so judge if it is secure to walk at night unaccompanied and with short clothes.
6. Trust your instincts – In some countries you will have to trust your own judgment to avoid dangerous situations and to profile people.
7. Look less like a tourist – It is not always feasible but it is a known fact that troublemakers prefer to attack tourists instead of local people, after all a tourist is much less likely to complain at the police station.
8. Learn a few words in the local language – It is something psychological: people feel closer to the ones who speak their own language, so if you learn a little bit of the local language, it can get you out of troubles in some cases.
9. Take time to adapt to a new place – The first days in a new place are more prone for troubles, you have to get used to the new environment and the behavior of the people.
10. Be careful with the traffic and other possible accidents. Everyone is used and expects car traffic to behave in a certain manner but it is not the same in all countries. In some countries cars ride on the “wrong side” of the road, in less developed countries there are almost no traffic rules.

Security in Risky Countries

Some countries and regions are known to be especially risky. For example, South America is known to have problems of physical attacks on tourists, kidnapping and drugs. Other regions in the world are in a state of war or experience terrorist attacks and some regions of the world have dangerous diseases. Take note of these:

1. In some cases the security problem for a certain destination is very real but in many other cases there is a psychological effect involved because of what was seen and heard on the media. Images of a terrorist attack when showed on TV are enough to prevent the flow of tourists to the place for many years, even when the danger is very reduced.
2. Once you will be in place, you will feel much better than before starting your trip. At your destination you will see people going on with their normal lives, you will see other tourists and even women going alone at night and so the warnings you have heard will get into proportion and you will feel better. (The scariest thing is to hear the warnings of your family before your trip).
3. Judge if the destination is very dangerous or just a little bit risky. If it is mildly risky you should consider visiting by making some adjustments. For instance you could decide that it is safe to visit the countryside but not the big cities. You could decide that it is safer to travel with airplanes but not with buses and that it is safer to travel in group and not alone. Try to reduce the risks, you can not eliminate them completely.
4. Read travelers’ comments about your (risky) destination in forums such as TripAdvisor. Take note especially of the comments of the expatriates who are living in place, they know better. Tourists who didn’t experience any security issue during their visit will tend to describe the country as a great place and that the danger is overestimated, while other unlucky tourists who were robbed or attacked during their stay will recommend not to visit the country at all. You can not really know the real statistics about getting into troubles from the written comments but you can get an idea. (Many people are not writing in forums about their experiences so the statistics are twisted).