Attire
Dress the part. Make guests come in true beatnik form by wearing beatnik-inspired gear: black berets, black and white horizontal stripes or black turtlenecks, Capri pants for the ladies, and black pants for the guys. Guys can wear fake goatees, and ladies can clutch cigarette holders. A neckerchief is also a must for any good beatnik, along with dark sunglasses.
Convert Your Kit
Use an existing murder mystery kit, or purchase one if you need to, and change the characters to beatniks. You can have fun beatnik names like Mr. Cool Cat, or Ms. Jive, which are inspired by popular terms from the beatnik culture. You can even feature famous beatniks like Jack Kerouac or Allen Ginsberg.
Give Snaps
A famous beatnik move was snapping the fingers instead of clapping your hands. You can incorporate this into your murder mystery game as well. Anytime someone is murdered, or gets an assumption right, guests can snap their fingers in approval.
Music Theme
Play artists of the beatnik generation in the background. You can throw in some Beatles, Bob Dylan, Billie Holiday, or really anything from that time that's poetic. And have a pair of bongo drums on hand. Don't play the music too loud in order to keep focus on the game at hand.
Create a Coffee Shop
Convert your dining room into a coffee shop. Coffee shops were home bases for beatniks, a place where they could share thoughts, ideas, poetry, music and art in general. Try dimming your lights and adding some candles, cups of coffee and dark furniture.