1% normally
3% if I'm watching p0rn

When the bar is yellow

Leaving a lithium-ion battery powered smartphone charging overnight is fine.

I NEVER leave the Horse with less than 100% (i could do with 90 on a hurry), so whenever I know I gotta go I charle it regardless of It's %.

3%

2% if I'm at home. 10% if I'm out somewhere.

Around 20%

between 30 to 50

My phone is really weird. Like, sometimes it dies at 20%
So I have to end up charging it 10-20%

Whenever I feel the need to
If I'm home and watching shows on it then it's usually plugged in regardless of the percentage left

30-40%. HTC is horrid

Whenever I go to bed, so from like 1%-40% depending on how boring classes were

My phone, I let it die and won't charge it until days later.

This

My iPhone 6 is always plugged in to my Mac during the day for work. If I step out it's always 100%. The lowest I think it has ever gotten to so far is around 70%, with the exception of every month or so I let it run down to 0% to calibrate the meter.

Then I leave it plugged in overnight, which is perfectly safe using OEM chargers.

One trick to save your battery is if you are using a case and notice the phone is getting hot during charges; remove it from the case, excess heat can affect the capacity.

Lastly don't store you phone/iPod fully discharged for more than a few days, certainly not more than a week, it can enter a deep discharge state. With a lithium-ion battery you can drop it below its low-voltage threshold, rendering it basically dead. It isn't actually dead but recharging it can be dangerous so there are safety circuits in place that will prevent charging and having it blow up in your face.

You can also damage your battery leaving it fully charged for long periods of time.

So if you are going to store your iPhone/iPod or any lithium-ion battery for a few weeks/months leave it at 45-55% and turn the device off.