If you've got the time, and the patience, we'd recommend waiting a couple of hours, especially with slower machines – go and cut the grass or watch a movie.
It may seem extreme, but you don't want to start meddling with these fundamental processes unless you really have to.
Speaking of running smoothly, however, these updates don't always do that.
In recent versions of Windows Microsoft has tried to make the process as pain-free as possible, but with so many hardware and software configurations out there, there's always the chance that some unexpected problem will crop up.
We're going to cover a lot of ground here for several versions of Windows and a variety of 'stuck' scenarios, so you may have to tweak some of these steps to suit your situation and software.
The first point to make is that interfering with updates that aren't actually stuck can cause a host of problems, so you want to make sure they really are stuck.
This can cause issues itself, so make sure your updates definitely aren't progressing at all.
In Windows 10 you can find the Windows Update page by launching the Settings app from the Start menu and clicking Update & Security – if there's something wrong and Windows knows what it is then you should find details here.
You're not going to break anything by doing this – these are just temporary files Windows creates so it knows where it's up to, and Windows Update will create them again from scratch.
With that done, go back to your command prompt window and type "net start wuauserv" (Enter) then "net start bits" (Enter) to get Windows Update and its related background services up and running again; hopefully this trick should be enough to kick-start the update that was previously stuck.
One of the more obscure reasons why a Windows update might not be installing is because a virus or some kind of spyware is blocking it: malicious apps like these can often be squashed by Windows security updates, which is why they try and stop the latest patches from being installed on your machine.
Try running a full and thorough virus scan using whatever security software you have installed (you do have some installed, right? If you think your antivirus tool has also been compromised you can download some on-demand scanners, like this one from Microsoft or this one from Dr. Restoring key Windows files and OS options is a lot easier than it used to be, and 'resetting' Windows 10 basically means putting all the system files back to their factory state without touching your personal files along the way (although you can choose to wipe your drive completely if you want).
Windows 10 has actually streamlined the update process, so you should be seeing fewer errors.