I see too many of us experienced folks answer a question with "research, know what your doing". Take the time to tell each person the basic rules without all the technical lessons, they've taken the first step to ask, many will not or even have a hard time "researching". Think of it as a small way to PIF. Something like this:
Battery Basics for mechanicals:
Buy good batteries from proven suppliers, there are many clone batteries that don't meet spec of the model they are cloning.
Know the maximum continuous discharge amp rating.
Don't exceed 70% of the max amp rating.
Use an ohms law calculator, Use 4.2 volts in the calculator, this is the typical voltage of a fully charged battery.
Ohm's Law calc
For example:
AW IMR 2000mah 18650 battery has a max continuous discharge rating of 10 amps. 70% = 7 amps.
AW IMR 1600mah 18650 battery has a max continuous discharge rating of 24 amps. 70% = 16.8 amps.
Using the calculator linked above for the 2000mah battery, put 4.2 in volts and 7 in for amps and you'll find you need to run a coil at .6 ohms or higher. The same calculation with the 1600mah battery, using 4.2 volts and 16.8 amps shows you can run coils of .25ohms or higher.
You also have to make sure that all the components of the mod or PV you are using can handle the amp load. Some have been built with switches that can only handle 3 amps. On a mod like this no mater what battery you have the lowest coil you could run would be 1.4 ohms.