3. If you're under-educated and / or have reckless tendencies - AVOID MECHANICAL MODS! If you are well educated and aren't a reckless person - then by all means, use a mechanical mod WITHIN LIMITS!
4. If you use a device that uses external batteries - DO NOT PUT LOOSE BATTERIES IN YOUR POCKET! Put them in a solid case that protects the entire battery! Don't put them in a "silicon sleeve", that leaves the side of the battery exposed and any damage to the wrap increases the chances of a short.
5. Keep your batteries out of extreme weather. Don't leave them in extremely cold weather and don't leave them in extremely hot weather. TAKE THEM WITH YOU - EVERYWHERE! Leaving them in your car in the summer may cause damage to the cells.
6. BUY PROPERLY RATED BATTERIES FOR THE DEVICE(S) YOU'RE USING! If you are planning on going cloud chasing, I suggest a 30AMP battery, hands down, every time, all the time. If clouds aren't your thing, and you're vaping at "reasonable" power levels, then shoot for a 20-25AMP battery. If you're using a coil / coil head rated above 1.0 Ohms, then a 10-15AMP battery should suffice.
7. KNOW YOUR DEVICE, KNOW YOUR ATOMIZER, KNOW YOUR BATTERY, AND KNOW YOUR LIMITS! This is self explanatory. But I'll delve into it anyways.
7a. If you're using a mod that runs in SERIES ONLY, then KNOW THAT YOU WILL ALWAYS NEED 2 OR MORE BATTERIES! Those batteries will need to be charged at the same time, used at the same time, and ALWAYS DISCARDED AT THE SAME TIME!
7b. If you're using a hybrid / pinless mod, make sure your atomizer has a protruding pin. Also, ensure when you clean your atomizer, you ensure there is NO DEBRIS LEFT BEHIND! No cotton, no wire clippings, no "gunk" - NOTHING!
7c. When buying batteries, use a marker and date them. Date the first time they were discharged and recharged. After a year or so passes, toss them and buy new ones. BUY THEM FROM A REPUTABLE SOURCE! DO NOT BUY THEM FROM EBAY, AMAZON, ETC! If they're still within reasonable age, but the wrappers are torn, scratched, cut, etc. Get them rewrapped ASAP! If the can (the silver part beneath the wrap), the positive ring, or any other part of the battery is dented, punctured, etc. toss it and buy a new one (or a new set if the batteries were paired up).
7d. Know your limits - what are you willing to do / what are your plans with your ecig, and what are you hoping to gain? Ask yourself this every time you do ANYTHING and all will be well.