There are courses and modules that cover nearly every risk they may face, but the education process would be long and laborious if we took that approach. In Istanbul alone do you prioritise terrorism, social unrest, scams, petty crime, official-looking but unroadworthy taxis?
Vigilance (being aware of ones surroundings) is their best defence against most of these risks and the best thing is that they only have to adopt a mindset against one of these risks, say petty crime, and their increased alertness will protect them against all the others as well.
Criminals and terrorists are constantly scanning faces and people, looking for targets or to see if anyone is observing them. By paying attention to the people in their vicinity and looking at their faces (without starring) they can see whether they have an intent or purpose and give themselves time to take evasive action. Additionally they are letting them know that they would be better off targeting someone else.
For your vigilance to work best they should still understand destination risk and where it is most likely and adopt best practices – for example not lingering in busy areas or not walking after dark. And whilst vigilance can help them avoid most risks they should still have a basic understanding of how to react to incidents they may face, such as what to do in the event of an explosion, see below.
Travellers should try and remain vigilant at all times – it is their best defence against inadvertently becoming a victim.