Excellent instructional video on the Ippon Seoi Nage. That is one of the most used throws in Judo and now in Jiu-jitsu.
In the video, you will be able to see a step by step approach to the Ippon Seoi Nage. Although a basic throw, it is still really technical.
If you are not able to perform all of the steps like getting your opponent off balance, correct entry, and utilizing good leverage, the throw will not work regardless how much strength you use.
It is critical that you create a reaction to achieve action or vice versa. The reaction would be the disruption of your opponent’s balance thanks to you. An action is the attempt of the attack itself.
One thing worth paying attention to is the position of your shoulder relevant to the other person’s which Sensei Sampson discusses in more detail.
There are many pieces to this throw that need to happen simultaneously so be patient. I would recommend practicing the entry by itself for a while before you even begin throwing.
Keep an open mind and never stop learning.