It’s worth investing in a battery charger to prolong your batteries' life (even if your mod has a micro-USB port). Without going into details, they give your batteries a better charge and don’t shorten their lifespan as much. The charger is bought separately, costs around € 20, and will serve you for years to come. The standard options are Nitecore (for example, the i4) and Efest (LUC V4 or V6). Nitecore can also charge a plethora of other battery types; this has nothing to do with vaping, but can be useful otherwise.
If you charge via micro-USB no matter what, try at least not to vape while charging. Box mod chipsets don’t like this, and there’s a chance that your mod will fail or even explode. There have been instances.
Treat your batteries with care so as not to worry about their well-being — don’t drop them and don’t knock them against each other. We’ve already published an in-depth guide called "Why batteries explode and how to avoid this".
Yes, we already hear the logical question: "Okay, I don’t get it, which batteries do I buy?". Get the Sony VTC5A, they’re good. Or Samsung 25R, these are also not bad, and the price is slightly lower. Tesiyi 40A are great batteries, but it’s near impossible to find them for sale. In general — make sure that the continuous discharge rate isn’t lower than 20A, don’t buy clones, and you’ll be just fine.