Things You'll Need
Instructions
Decide which person will play as the Dungeon Master and which person will be the player. Both people should be honest with each other about how much work he or she wants to put into the game because the Dungeon Master is responsible for creating the entire campaign and running the entire adventure for the other player. The person who enjoys being in charge, playing various nonplayer characters and monsters, and being the narrator, as well as having the responsibility of planning the adventure should be the Dungeon Master. The player who wants to fill the shoes of a single character that he or she will shape over the course of multiple adventures should decide to be the player.
Roll up a character, using the dice and the instructions provided in the "Player's Handbook," for the player. The player and the Dungeon Master should discuss the background of the character, his or her physical and mental traits, and the character's personality. Things like race, class and attribute abilities should be decided as well. Once the character has been created, the Dungeon Master should begin to think about how he or she can use the player's character as the center piece of the campaign.
Plan the campaign using the "Dungeon Master's Guide" and the "Monstrous Compendium." The Dungeon Master has to create a world, using the background, personality, and role of the character created by the player. The Dungeon Master should create a number of nonplayer characters for the player to interact with and perhaps to even join the player on his or her quest. This way the various skills of different character classes will be present for the player to take advantage of on the quest. The main benefit of playing with only two people is that the campaign can revolve specifically around the player's character.
Play out an adventure. Once the game begins, the Dungeon Master can choose to use predesigned solo adventures. These can be easily found by searching "D&D solo adventure" online. Some are even freely available for use by their creators. The main key is to make sure to tailor the adventure to the background and personality of the player.
Build upon that first adventure. Once the player has had a chance to let his or her character grow, the campaign will begin to flesh itself out. By letting the player have free will over where he or she chooses to explore and who he or she interacts with, the Dungeon Master will have an idea over what aspects of the campaign will have to be more fully developed when planning future adventures.