[Shamie]

Some know quite a bit, and some know hardly anything at all, but a runner doesn't survive long if he continues thinking of magic in the way that the trids portray it.

though "geek the mage first" is a classic.

[ZeConster]

Note to self: next time I summon a spirit, spend a service on "pretend the Tank is your summoner while still obeying my orders".

[Elektrycerze3]

Note to self: next time I summon a spirit, spend a service on "pretend the Tank is your summoner while still obeying my orders".

Hm... That sounds like a nice tactic. Why not even dress your tank in some faux-magic clothes, like robes with lots of weird trinkets?

[Icy]

Being a professional, a runner should always know everything a mage could do to screw up his job.
This doesn't mean he has to know magical theory (although it's an interesting hobby ofc), but at least the practical uses of magic should be known.
What dangerous spells and spirit powers are available? How does the line of sight for spellcasting work? Where can a projecting mage follow you? Where not? What terrain makes assensing more or less easy? How much firepower do you need to fight the average spirit of a professional mage? And so on.

It also helps to learn the counters against magic. Where can you expect background count? How do attacks of will against spirits work? Where on the black market can you get the magical compounds from Street Magic and Arsenal? Stuff like that.

If your runner is more interested into magic than these basics and maybe wants to try it out himself:
There is alot of magic that even mundanes can accomplish. I already mentioned magical compounds and attacks of will. If you just need assensing, you can also try Tempo at your own risk. There are also  rules for summoning and binding of free spirits with their formula (possible without binding skill), the rules for calling wild spirits from Running Wild (only Arcana needed), and of course detection spells, for almost all of them are a kind of buff that can be applied to everyone. The same goes for loaned spirit services and anchored spells, although the latter is pretty karma intensive for the mage if you don't possess an anchoring focus.

Then there is magical theory and the Arcana skill, which can be learned by everyone.

Rich people with enough money to buy magical compounds en masse can almost be a sort of awakened by the pure power of their purse, for the rules say that any critter power (and even projection for 1000Y per use) can be provided by these compounds. Keep that in mind when you encounter these corp execs. We had a very rich wife of a NeoNET executive who was a mundane wiccan. She communed with spirits and bought alot of compounds and was therefore a kinda competent magic user. She also studied magical theory and gave our mage a lesson in Arcana.

[Reaver]

taken from the opening pages of Street magic for 4e (circa 2072)

Word on the Street :
What Does Magic Mean to You ?
(asked at: Aurora Mall, Seattle)
Mary, 24, New You Employee, Seattle: Magic
is scary. I mean, those people can do whatever
they want to you. They can read your mind, fry
your brain, or watch you when you’re taking a
shower or having sex. And you can’t even tell
who’s magical and who’s not.

Franklin, 18, Student, Seattle: What does it
mean to me? It means power. I’m from the wrong
end of town, but I got tapped by the Mitsuhama
college recruiting program and I’ll have a great
job waiting when I get out, just because I can
summon spirits and cast spells. It means respect.
It means nobody messes with me.

Ethan, 54, Middle Manager, Chicago: It’s unnatural.
Miracles and magic are the province of
God, not of man, and one of these days all of
these blasphemers are going to find out just
what kind of fire they’ve been playing with.
Li, 42, Mystical Consultant, Hong Kong: Magic
is a gift. It’s a way to be closer to the natural
forces around us—to work in harmony with
them to bring about beneficial change. Magic
is not a thing to fear, but a thing to embrace.
Corrine, 40, Lone Star Officer, Seattle: Frankly,
magic is a pain in the ass, especially when it’s
on the wrong side of the law. It’s hard to stop,
hard to catch, and hard to deal with once we
do catch it.

Rain, 22, Eco-Activist, Seattle: Magic is a way
to be one with nature, to see firsthand what
the corps have been doing to our mother Gaia.
Anybody who’s magical and doesn’t support
the fight against the rape of our planet doesn’t
have a heart.

Tetsuo, 20, Athlete, San Francisco: Never
mind spells and spirits. Magic is about being
in tune with your body. When every muscle is
under your complete control, singing with the
mojo, letting you do things that mundanes
can’t hope to match—man, who needs drugs?
It’s the ultimate high.

[Red Canti]

The absolute minimum is being able to identify when someone is about to use a spell.

It's a lesson you learn quick the first time you watch someone get burnt to crisp or turned to mush.

[Malathis]

I think it's largely a charachter concept issue, any given charachter can know as much or as little about magic, with reasonable upper end limits. Low end, a charachter simply never paid much attention real magic users maybe never watched the magic trid's to see what media says they can do, or wholly believes everything the trids say can happen. High end, they've been around the block a few times had long discussions with friendly mages/shamans, maybe read a few wikipedia pages or other types of articles on magic, but not to the extent of actually having a magical theory rating. So they know that theres a wide variety of effects that magicians can do but a single magician probably can't do all of them, and that thier are certain more advanced techniques that can increase a magic users abilities, but these are rare.

In short, again it's completely up to the individula charachters background story.

[Michael Chandra]

Note to self: next time I summon a spirit, spend a service on "pretend the Tank is your summoner while still obeying my orders".

Hm... That sounds like a nice tactic. Why not even dress your tank in some faux-magic clothes, like robes with lots of weird trinkets?

Works really nice when you use a non-visibly-augmented tank.