Have your character – or characters – surrounded by clouds or smoke, completely divorced from any kind of earthbound reality.
Your characters – or at least one of your characters (Anna Faris in Smiley Face, James Franco in Pineapple Express) – should display a goofy euphoric grin.
Remember, stoners do not dress well. Faded blue jeans and sneakers are preferable attire.
Be sure to come up with a cute coy catch phrase that lets the public know your film is about smoking and getting high. Something like, “High. How are you?” (Smiley Face), or “Put this in your pipe and smoke it.” (Pineapple Express).
“Bromance” is generally a subtext in the successful stoner film, so make sure your main characters are male. Smiley Face was one of the funniest stoner comedies ever made, but nobody went to see it ’cause it starred a girl.