This first video will get you started with finding peace, harmony, and a balanced prop the quickest. Watch all videos if you choose and you'll find that each has merits and demerits. For example, the first video does a GREAT job of demonstrating checking the tracking of the prop first (merit). But, the concept of balancing with velcro and super glue I find horrendous (demerit).
Now here is a nice series of 3 videos that's fairly comprehensive from 2 brothers hobby.
There are different approaches for prop balancing -- different paths to the same destination. Below I've included three more videos, to give you more information as you seek balance and harmony.
The next two videos are from Dubro - makers of the prob balancer you will see in all 6 of these videos. There are other very good balancers available.
You should know it all by now, but just in case here is one final video from our friends at Horizon Hobby.