After figuring out the guest list, food is the next major factor. A pot-luck style prevents you from getting overwhelmed, but you should specify whether you plan to have a sit-down dinner or just munch on finger-food all night long. Don’t forget the drinks, whether alcoholic or otherwise. Once you have the details hammered out, send invitations. A Facebook event is typically an acceptable way to manage a modern get-together, but some occasions do call for a more formal mailed invitation.
Small details can make themed parties extra special and set them apart from a regular hang-out session. Decorate if the occasion calls for it, and definitely create a playlist and serve food on your nicest plates.