Here's what I post to those just getting into Mech's -
1. Ohm's law,
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2. Batteries! you MUST take good care of your batteries and know them!!!!!!!!
a. Avoid garbage batteries like eFest who rewrap rejects with grossly inflated amp ratings. Stick with authentic LG, Sony or Samsung from reputable (not ebay or amazon) sources, great places to get authentic are from
Liion Wholesale Batteries | Li-ion battery/cell distributor
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b. Stick well within Continuous Discharge Rate (CDR) Not the "pulse"
c. Keep up to date with what Mooch tests and battery ratings, follow his posts on Facebook and his Blog
d. In Mod's with multipule batteries, marry them.
e. Get some battery wraps, they're cheap and easy to re-wrap batteries. Any nicks,tears or what ever don't be stupid and just re-wrap.
3. Don't build stupid low a good builder can chuck and get awesome dense vape from a good build. It's simple, with 20 CDR Amp batteries -
a. Single battery mod's you're fine with .2 ohms on up
b. Dual Parallel you're fine with .15 on up. Parallel you take the full CDR of one battery and you can add 1/2 the amp rating of the next battery
c. Series you double the voltage but you share the amp. So a series you build high with a lot of wire, no lower that .4 ohms.
4. Make sure you don't have any shorts. For an extra caution any new build I vape on a regulated mod for a few drips or with a tank about a 1/4 tank. This is to insure nothing wonky with my build or any shorts.
5. Careful if it's not in your hand, if it doesn't have a lock on the button and you put it in your pocket (which I really don't recommend) insure nothing else is in your pocket and it's loose. Don't want to put it in your front jeans pocket and blow your Johnson off ya know

6. Last but certainly NOT the least, keep it clean! Clean it when you first get it "before" you even use it and clean it on a regular basis.
a. Ultrasonics are a very good investment, got mine off Amazon for around $25.