Get used to the combat, skills, and magic system first, if you aren't already, before moving to more complex systems like hacking and vehicle combat.
Keep the game moving. Try to have several mini shadowruns on hand at all times, which you can run if you run out of material or things seem moving slow. Even a simple run where everything goes right and there's no combat will focus player attentions and they enjoy picking up a little karma.
About the structure of a shadowrun:
A Shadowrun has 3 parts, the legwork part being somewhat optional. (Although some shadowruns are almost entirely legwork if you want to design them that way, such as a mystery that must be solved or a lost person found)
Nearly all shadowruns start with meeting a Mr. Johnson. Meeting the Johnson usually is done at a bar or night club of some sort, often in the back room, but this is not a set rule. There is sometimes a meeting with a Fixer first, but often this is done by phone/text. The runners get the vague outlines of the run, decide if it's something they want to do, and if so then negotiate a price. At this point the runners are given more details on the job and can ask questions. The Johnson sometimes provides help with the run or sometimes will provide it if asked. (Fake key cards for example to get in the target site) This is a great time for a GM to help out beginner players with ideas on how to infiltrate the site.
Instead of a dungeon full of monsters, shadowrunners penetrate security systems. This is usually to get into some building or group of buildings. The basics you need to have is a layout or at least a general idea of a layout, guard stats and patrol habits, command centers and other large groupings of guards, physical security (ie drones, cameras, motion sensors, fences, and more), magic security (if any), and matrix security (If any, usually at least a small amount) You also want response times both for the police and any additional security the site has contracted. (Could be their own forces somewhere nearby or some other contracted company) The generic shadowrun is the runners breaking into a building to get a hacker to an offline system to steal paydata. But sometimes the target is something physical. And kidnapping valuable employees for a "career change" is another common shadowrun.
The third optional part of a shadowrun is the legwork section. Not strictly necessary, but it makes richer stories and it lets certain character types like Faces get a moment in the spotlight. This is mostly meeting with contacts to get information about the run. It may involve solving a mystery or it may involve things like learning the physical layout of a target. Sometimes an entire shadowrun can be mostly legwork. For example, you are hired to find some rich corper's runaway son or daughter. (The legwork section of the run usually is set before the security system penetration) Sometimes this section includes stuff like the hacker trying to learn more about the target site using hacking, stealthy characters scoping it out, or magicians with astral projection scouting astrally.
