Be sure that all the muscles are warmed up first. Remember that in power lifting several muscle groups are involved. Contract each muscle group and use them all in lifting. This will avoid injuries. Before going to the gym avoid eating sugar, especially refined sugar products.
Sugar gives only temporary energy.
It is better to eat some natural carbohydrates with some fats as this body fuel. Your energy will last longer, and you will have increased power. Do not try to train when hungry or after a filling meal. However, if you are working and unable to train at this time, it is better for you to eat a light meal, then rest for an hour before going to the gym. You will be refreshed and feel as though it is the next day.