As always: this is just to get your started, and to give you some ideas on just what you can do.
Know what apps you’ve got installed
This matters a LOT for system speed and stability. A clean phone with as little on as possible will ALWAYS be much much quicker than one with lots of apps and things on it.
Even to have a clean gallery will help on speed and stability as well. Tends to be that the less you’ve got on it: the quicker it will be.
I’ve got four steps that sorts out most phones
1. Soft Reset
Simply press power button (volume up and power button on One M8) for 10 seconds with phone on and active, it will do a countdown after 7 seconds. And will after that do a nice clean restart. This you use if phone crash as well and just doesn’t respond as well.
2. Boot into Safe mode
This is simply boots without loading 3rd party things, perfect if 3rd party keyboards etc doesn’t work. On phones where you’ve got an external storage (like M8), folders and stuff on screens can go missed after a safe mode. Read about it HERE
3. Wipe Cache partition
A way to get rid of various odd issues with battery etc. Seen it been recommended by HTC. Esp One M7 around 4.4 update. Read about it HERE
4. Factory reset
To simply start over with the phone. This removes all user data and apps installed etc. It will however not revert installed update back to previous version. Just make that you have contacts synced first, as having your contacts on your google account is to recommend. I rarely backup apps etc since they can themselves be the problem. Read about it HERE