there is a perfect time for pretty much all methods.
vaporizer - i like the morning or late afternoon for the vape, especially if i've got a pot-friendly activity i'm about to do (running, biking, cleaning the house). clear-headed and active, but also really trippy. i generally don't like it as much for social situations, as anyone not used to a vape tends to get blown away by mine.
bong - stoner days with the stoner homies. sitting around on couches, watching tv or playing video games with no future plans that involve society or activity.
bowl - road trip. in the woods while skiing or mountain biking. late-night, by myself, in the back yard.
joint/blunt - lots of friends around. drinking. festive atmosphere. not just a "stoner party." even the "once a year" type smokers will take a hit sometimes.
and now, instead of studying, alll i want to do is get high as shit and go be outside. serves me right i guess.