1. Modern phones use Li-ion and Li-poly batteries. Their battery life is not affected by whether you charge them at 0% or 90% of remaining battery. However, it does have a long term effect. Batteries degrade with every charge cycle and cycle is usually a recharge from below 50%.
So charging while the battery capacity is still relatively high has a good impact on battery health and it results in long term effect of less degradation.
2. Avoid frequent full discharges because this puts additional load on the battery. Regular partial discharges with frequent recharges are better for lithium-ion than one full discharge. For prolonged storage, keep the battery at a 40% charge level.
3. Keep the mobile phone battery moderate or cool temperature. Avoid to charge in a moving car going at long distance.
4. Avoid purchasing spare mobile phone batteries instead of original one which comes in package box. Do not buy old stock or sold at clearance prices.
5. In some devices, accurate charge level is not shown which may be due to hardware or application problem. In this case, device gets overcharged every time. Try to use third party battery app to know the exact level of phone discharge.