Planning a 1940s party requires establishing a theme, and one such theme is a Hollywood theme. My Party Planner recommends sending Hollywood-themed invitations asking party-goers to wear a costume related to their favorite Hollywood stars from that decade, such as Humphrey Bogart or Joan Crawford.
Another way to give a party a 1940s Hollywood theme is to rent a marquee to place outside the party, roll out a red carpet and play "Casablanca" in the background. Another source of entertainment is to practice swing dancing either by hiring a few professional dancers or having guests try their own dances with swing music. Martinis, wine, champagne and even punch served in a crystal bowl complete with an ice sculpture in the middle round out the ambiance.
Another 1940s party idea is to have a raffle. The party-goers need to sign up with the "Secret Service," which was established in 1940, according to Quest Adventure Hunts. One way to do this is to act as though guests have been called off to war. This involves calling out the losers throughout the night, who represent new soldiers. The person left standing wins the prize. Options for guests' dress include soldier uniforms or pin-up girl costumes.