Buy A Roll Of Film

Field	Photography
Went Obsolete	2007-ish
Made Obsolete By	Prevalence of digital cameras over film-replacables
Knowledge Assumed	Film speed/exposure levels
When useful	When you need to take more pictures

Go into a convenience, grocery, drug, or photography store, select the type of film, number of exposures, and pay for it!

Note, those over 20 or so may still do this for a while, but the younger set probably never will.