The "relatively" safe method, barring a new machine, is to setup a second machine, and use it exclusively for a bit. This ensures you have everything you need on the second machine. At that point, upgrade the other machine.
The more risky method is to just go ahead and update your main machine. This assumes you have known good (AND tested) backups.
Candidly, I don't always follow my own advice. But, and this is a "large" but, I have many known good and tested backups I can restore from, and know I can restore - from scratch if needed - in a few hours at most. I have a reasonably current second machine at the ready at all times, an alternate collecting dust at my feet, I can "borrow" a different one from a family member, and if I really had to, I can get a new machine within an hour.
My former advice was to simply plan on (meaning budget time and $) for a new machine for each new version of Windows. This keeps your machine current as well as having a clean install of Windows. Still likely the best advice. While machines are not getting noticeably faster for the average user, there have been hardware security updates we all should use. Consider - a client asking what OS you are using, and what hardware - and whether or not you are current enough to be able to reply in a professional manner. Not professional, for instance, is "I am using 'insert dead OS version here' on a 5 year old computer".