Before anyone should start this process, you should know how to do the following-
1. How to get to Recovery Mode
2. How to get into Download Mode
3. Be able to perform the above at will
If you can't do those, you should wait until you figure that out first. Otherwise, if you run into any troubleshooting required, you will waste time figuring out how to do it while your phone is non-functional. Better to learn these steps while your phone is still working, so you can spend time fixing things instead of researching what needs to be in your brain already.
I speak from the voice of painful experience. You CAN learn those as you go, but you will be better served spending the time up front.