Battery - do they last longer if recharged when empty?
Modern phones use Li-ion and Li-poly batteries. So the battery life is  not affected by whether you charge them at 0% or 90%. 
It only has a long term effect. Batteries degrade with every charge cycle. A cycle is usually a recharge from below 50%. So charging while the battery capacity is still relatively high has a long term effect of less degradation. 

The other frequent pseudoscientific habit that has no roots is a technique many call "formatting", where you leave your battery plugged in for 16 hours or 3 * 8 hours with discharge in between or any other baseless claim by anyone on any forum or phone shop. If they don't have scientific evidence don't believe them.