I am lucky, in that there are no big predators (animalwise anyway) in my country. However, I would suggest following the same rules as if you were camping alone;
1. Always let people know where you are. If you will be in a remote area and you will be gone for for a few hours or more, or a good distance into areas with very low traffic, then contact the local authority and let them know.
2. If you need to leave the car, leave a note in the car and take the co-ordinates of the position of the car to find your way back.
3. Take a first aid kit, (for snake/spider bites and scratches etc), plenty of water, snacks and sunscreen etc. Take a map of the area if possible and spare batteries.
4. Take a phone, but also a whistle and mirror in case you need to signal but have no phone reception.
5. If you are really worried, try a defense class, or see if there are security devices (eg pepper spray) legal in the country. There are also special GPS's out there that (for a base cost of $600 and at bit extra each year) function as a 'personal emegency beacon'. Click the button and it sends out a distress signal to the rescue departments.
6. Try and avoid going in areas at times when suspicous characters are around, act confident like you are just waiting for someone. Try to keep valuables to a minimum or keep them less obvious in urban areas.
The advice already given about backing away when you don't feel safe is a good recommendation as well.