The five LiPo habits that prevent fires and dead packs: storage at 3.8V per cell, 1C balance charging, low-voltage cutoff, when a puffed pack is done, and safe disposal.
Five habits prevent almost every LiPo fire and most dead packs: never charge unattended, store at 3.8V per cell, never run below the cutoff, never charge a puffed or damaged pack, and charge on something that can't burn.
If you skim the rest of this, at least take these:
A LiPo cell is happiest sitting at about 3.8V per cell. That's 7.6V for a 2S pack, 11.4V for a 3S, and so on. Any decent charger has a storage mode that will bring a pack up or down to that number for you.
It matters because a pack left at full charge (4.2V per cell) ages fast. The high voltage stresses the chemistry, and a pack you charged Friday night and didn't run for a month loses real capacity just sitting there. I left a pair of 3S packs topped off in a drawer over a winter and by spring they were puffed and down about a third of their runtime. That wasn't bad batteries, that was me.
So if you charge a pack and don't end up running it, put it back to storage. Leaving it full overnight because you're running tomorrow is fine. It's the weeks that kill them.
Charge rate is measured in C. 1C is a current equal to the pack's capacity, so a 5000mAh pack at 1C is 5 amps. I charge pretty much everything at 1C and only push higher when I'm at the track and need a pack turned around between heats. Plenty of modern packs handle 2C fine, but faster charging runs hotter, and heat is what wears a pack out.
Always balance charge. Plug in the main lead and the little white balance plug, every time. That keeps all the cells at matching voltages, and cells that drift apart are how packs get into trouble. Skipping the balance lead saves you ten seconds and costs you a pack eventually.
The charger matters too. Any modern balance charger from a known maker (ISDT, SkyRC, ToolkitRC, Hitec) will do. If you're still using the little one that came bundled with a starter kit, that's the first thing I'd upgrade.
Puffing is when a pack swells up. It's gas building inside the cells as the electrolyte breaks down, and it doesn't reverse. A puffed pack stays puffed.
A small puff on an old pack with a lot of cycles on it isn't an emergency, it's the battery telling you it's near the end. You can usually finish out its life gently, storage charging it and keeping an eye on it. But a pack that puffs suddenly, or gets hot in your hand, or won't sit flat anymore, is done. Same goes for any pack you crashed hard enough to dent or poke a hole in. Physical damage to a LiPo is how fires start, and no pack is worth your house.
A LiPo safe bag is the minimum. They're ten bucks and they buy you a lot of margin. I've moved up to a steel ammo can with the gasket cracked open a little so pressure can vent, and it lives on the concrete floor in the garage. The idea is that if a pack does let go, the fire is contained and there's nothing around it to catch.
And don't walk away from it. A failing pack usually gets hot or starts to swell before it vents, and someone in the room can get it outside while it's still just hot. If you haven't chosen between chemistries yet, NiMH vs LiPo covers it.
The old forum advice was to drop a dead pack in a bucket of salt water for a week. Don't. It corrodes the terminals, it can generate gas, and it doesn't reliably take the cells to zero anyway.
Discharge the pack fully, then recycle it. Some chargers have a discharge function that will take it down low. Otherwise put it in a car and drive it dead, then let it sit and finish going flat. Tape over the leads and take it to a battery recycler. Most hobby shops and the big-box hardware stores have a lithium bin, and Call2Recycle drop-offs are all over the US. Don't put a lithium pack in your household trash.
Treat them this way and a decent pack gives you a few hundred cycles over several years. When runtime drops sharply or a pack starts puffing, retire it. A tired pack sagging under load makes a good motor feel gutless, and you'll waste a weekend blaming the wrong part. Storage-charging belongs in your post-run routine, and more common questions are answered in the FAQ.