If you want you can get strong, but it is optional. It would probably help though. You also need a good angle going up on the ball. If you swing down on the ball you will hit a grounder. If you swing straight that might work but if the wall is high you would hit the wall. You also need to line up your knuckles on the handle of the bat. You can if you want to choke up for speed an inch,but that could take more power out of your swing. Make sure that the pitch is in the strike zone (you have a better chance of hitting a home run). The strike zone is your knees to the bottom of your chest and over the plate. You should bend your knees. Some players like to bend their knees a lot (it makes the strike zone smaller). Look at where the ball is released to see if the ball is going to be high or low. When you are swinging keep your arms and hands level. Also focus on the ball.Also when you are swinging coil your lower body and bring the bat around your body.Then drop the bat and run to first (don't throw it). When MLB players hit in the home run Derby pitcher through the ball 20 miles per hour lower than a regular pitch.
Here is a video of MLB players hitting home runs(it is not just home runs):
Here is a video of MLB players hitting home runs(it is not just home runs):
This is more specific facts that are harder to explain on hitting a home run: