A forbidden deed, a severe & serious major sin after shirk and murder. The punishment for Zina is the most severe of punishments, because it violates peoples’ honour and lineages.
Al-Hafiz Ibn Hajar RA said: Zina is not always associated with the private part itself, but may involve other faculties such as the eyes and so on.
Do not even come close to Zina, don’t do any deed that may get you close or lead to Zina.
Do not be alone with a member of the opposite sex non mahram, touch, look or go to evil places.
Do not speak in a haraam manner to whom one is not related, thinking and planning immoral acts, and so on.
Be the slave of Allah
“And those the servants of the Most Merciful, who never invoke any deity with Allah, nor kill the soul that Allah sanctified- except by right, nor commit Zina. [al-Furqan 25:68-70]
And
O you who have believed, do not follow the footsteps of Satan. 24:21