One answer states: "logon to your router's config page and update its firmware, it only takes a few minutes"
This is bad advice. Don't make this choice lightly. Make sure you have an actual real reason (ie the release notes specifically say it fixes your problem) and not just a hope that it might make things better.
Certain companies firmware upgrades (eg Netcomm) have a track record of unreliable flawed upgrade procedures and will often leave you with a dead equipment, EVEN if you follow the documented process carefully and in detail.
But the biggest tip, before doing anything else, is do a Google search for "your equipment name" firmware, and see how many others have tried an upgrade and had problems with that equipment. Also include the version you are upgrading to, to see if there are problems specific to it.