Things You'll Need
Instructions
Pick a time and place for the story. Whether your are in Los Angeles or Seattle and whether the game is before or after significant events can impact the story. Nailing this down allows you to determine what resources and obstacles your runners may face.
Prepare scenarios in broad strokes. Unlike some games, Shadowrun offers a world with a plethora of options. Determining too much detail ahead of time can bog you down. The "hook, line, sinker" method works well for a starting GM: The runners receive an assignment, they execute their cunning plan and some type of twist occurs.
Create non-player characters (NPCs) simply. Use the NPC rules in the "Shadowrun Core Rulebook" Friends and Foes section, and use the templates for grunts and squads. If the characters come across an NPC runner, use the guidelines in the Friends and Foes section to determine how powerful the NPC appears. Many free spreadsheets are available online for simple character creation for both the GM and players.
Read your players' character sheets, and know the characters' skills and attributes. Don't anticipate or expect your players to live up to moral standards that they don't explicitly state for their characters. Runners in the shadows are criminals, pure and simple.
Force players to use their connections. Who a character knows is key in Shadowrun, but most players don't realize that until it's too late. Give the contacts personality, and have players interact with them to get what they desire. Then make the appropriate dice rolls to find whatever is needed based on availability and the contact's connection rating.
Memorize the basics for each class. One of the consequences of having so many aspects meshed into the same world -- technology, magic, corporations and mystical creatures -- is that each class essentially has its own system. Require the players to know all their specific roles and the rules for their characters.