What to know before Dual Booting Windows + Linux?

I'm looking to finally use Linux properly and I'm planning to dual boot my laptop. There's enough storage to go around, and while I'm comfortable messing around I'd rather not have to run and buy a new device before school while fixing my current one.

https://m.youtube.com/watch?v=VaIgbTOvAd0

This was the general guide I was planning to follow, just with KDE Plasma (or another KDE). I was going to keep windows the default, and boot into Linux as needed when I had time to learn and practice.

I assume it should be the near similar process for KDE Plasma?

I'm ok with things going wrong with the Linux install, but I'd like to keep the Windows install as safe as possible.