Choose a performing persona. The great magician Jean Eugene Robert-Houdin said "A magician is an actor playing the part of a magician," and this is essentially true. Every successful magician portrays a character when they perform.
Evaluate all potential magic tricks for a performance against the character that is being created. Simply ask if it makes since for the character to perform these magic tricks. For example, a mad scientist character would probably not mesh well with card tricks while a riverboat gambler would.
Establish a link between the selected magic tricks. The overall goal is to create an entertaining routine with magic tricks that flow together in a sensible manner. It is often helpful to establish a theme to connect the magic tricks.
Arrange the magic tricks in an order that maintains the entertainment but allows for the "dirty work" of magic to be accomplished. For example, if an effect requires a live weasel to be strapped to one's chest, the weasel should be produced and freed before the effect that fires a cannonball into one's torso. More realistically, if a trick leaves one with wet hands, do not follow it with a trick that requires precise control of cards.
Acquire the proper wardrobe for the character being portrayed. Make sure that any required props make sense for the character as well.
Study acting and, if the performance is meant to be funny, study comedy too. If seriously pursing magic as a career, take classes in performance skills and stage craft.