For people who care about this, I would recommend float charging at 40%, slow charge to 60% before use, then slow discharge to 40%, preferably all done at 10 degrees C. And, for safety reasons, you should ideally have supervised charging in a fireproof bunker. Empty fireplaces and concrete basement floors can work in a pinch.
If you don't care, just use your device normally and buy a new one when the old one's cycle life starts to suffer.
If you want to be somewhere in the middle, try to plug it in reasonably soon after it dies, or ideally before it dies. Keep an eye on your devices on the first charge after you buy them, and on the first charge after a drop or impact, watching for smoke, burning plastic smell and swelling. Don't attempt to charge a swelled battery, and dispose of lithium ion batteries properly. Disclaimer: All the above advice is given without warranty, do your own research and don't rely on this advice for your safety.