When I used to do it, we all used to either stay on at work and drink, or go back to each others houses and go till we crashed. Sometimes we would head off to the beach for a bbq. We all were and still are quite a tight nit group of friends despite all moving on to pastures new.
Working nights is different kettle of fish though, you are gonna have to train yourself to either get up and go straight to work and have your wakey time aftet your shift, or go straight to sleep once you have finished. You never get the right quality of sleep when you are working nights and your social life will suffer no end. Sorry!!