This is probably something you will figure out, by the time you hit level 25. But if you are just starting out, then let me help you out a bit. I carry 4 rings in my pack.
The first 2 are Fire Resistance rings. The second ones are Lightning Resistance rings. While at level 20+ I have yet to really come across any mobs which will have me dying from the cold, it is on my list of what I need to be carrying. Soon I will have 2 +Fire resist, 2 +Lightning resist, and 2 +Cold resist rings.
Why? because when I come across a fire caster, I can switch out my rings fairly quickly, which in turn allows me to run straight at the mob, rather then trying to kite them, while in turn I am being Kited, and the same goes for lightning casters. Without the rings, I need to run in, kill a mob, run out, regain health and energy shield, and then rinse and repeat until I can down all the mobs. With the rings, I can quickly take them down.
Tip: Search your passive skill tree, and try to find a way to increase your resistances that way as well. Those 3 resistances, will be a boon to your character’s survival if you have them.