Drinking and smoking are both acceptable and common. It is not polite to be excessively drunk in public, but it is not uncommon, though usually it is people who are unemployed, not students, who show such behavior.
Namibian men tend to be very forward and very persistent. Namibian women play hard to get, usually turning down a man numerous times before accepting an invitation. “No” does not actually mean no as it does in the west; it is considered part of the courting game.
Women should be strong and forceful when saying no in order to make themselves clear.
Actual dating in the western sense is not very common in casual relationships.
Casual sex is common and should be avoided by foreigners and visitors to Namibia, at least in the beginning. Not knowing the country and its people well puts visitors at high risk, so such activities should be taken with caution.