The cross will be one of your harder punches, because it will be your dominant hand, if you are an orthodox fighter, the right cross is your strong hand and if you are a southpaw, it will be the left cross. Use the tips in the video below to increase your punching power.
Just like the jab, keep your elbow higher than your shoulder.
Dip the opposite shoulder.
Take your head off center to avoid any possible counter from your opponents right cross.
Also not mentioned in the video but should be common knowledge, raise your back heel as you are throwing the cross and keep your non punching hand up.