This is to be seen as a starting point more than anything. But, you will be able to sort out most little “kinks” this way.
Lets cover the most important thing first: Having issue with a phone (like crashing etc) after a major update does NOT mean that the update is “bad” or “full of bugs”. If your friends tells you that, then you need to replace your friends since they’re broken (or they need a new firmware).
I will assume Lollipop update now, since that is what’s going around for the moment. And that you’ve got a HTC phone.
You have an article with generic troubleshooting HERE, if you want to try with that first.
I recommend that you do a factory reset if you are having issues, as simple as that. Yes, that will sort out all kinds of issues.
Following is written around M8 running Lollipop, but works for all HTC phones.
Simply follow the instructions HERE. It will of course take a while to setup your phone again, but it’s so worth it.
Wipe Cache Partition
Simply follow the instructions HERE. This step will not remove any personal content on your phone, it will merely make sure that the environment on your phone is as nice and clean as possible.
Issues with Facebook Messenger
You have no Developer options under Settings? Follow THIS
You’ve got a little more HERE