If you know that you are going to be outside in the rain and there is every likelihood of you having to call on, or answer your phone, put it in a plastic zip lock bag.
You will still be able to push the letters and hear it ring without getting it wet.
Scratches on your screen can be inevitable, even if you have a case for your phone.
This can really spoil your photos too.
So, make sure you cover it.
There is a special kind of non adhesive clear vinyl screen protector designed especially for cell phones.
You will find it at stationery shops, cell phone retailers or camera outlets.
Every now and then run your battery down completely before recharging it.
Never simply put it on recharge every night.
This will mean that sooner, rather than later your battery will need replacing.
Overcharging can be worse than undercharging your battery.
If you leave it charging for over 12 or so hours your battery can overheat and damage the phone.
Source Don’t Throw it out: Yankee Magazine