to swing for the fences, but remember to also press up on the left analog stick along with
to swing upwards (known as an "uppercut" swing), increasing your chances of getting a home run. Also, be sure to swing as the ball crosses the plate for best results.
Choose someone with a high Overall AND high Power. Jose Bautista of the Toronto Blue Jays has a 98 Overall AND a 97 in Power, making him the best choice for a quick and easy 100%.
Like the actual MLB Home Run Derby, failing to get a home run counts toward your total "outs", and your round ends at 10 outs. However, you can "take" (not swing at) a pitch without it counting as an out, so if your pitcher doesn't throw one down the middle of the plate, lay off until the next pitch.
Just like the trophies say, DO NOT switch sides or fast-forward at any time, as that will nullify your chance of getting the trophies.
In other words, do not visit the pause menu at any time as that is where these options are found. Also, make sure the match is against the CPU and not against another player, as trophies only show in matches against the CPU.
To explain some common baseball terms that a newcomer might not know:
The "foul pole" is the giant orange poles on the left and right sides of the field. If you hit left of the left field pole or right of the right field pole, it is a foul ball and therefore an "out". However, anything that hits the foul pole is a home run.
The "power alleys" are halfway between the foul poles and the middle of center field where the 408ft sign is. These are where most home runs are hit to, hence the name "power alleys".