You absolutely need to know about the Wiggle if you ride your bike in the city. The 2006 SF Bay Guardian puts it as "Remember how...relieved you were to discover it wasn't necessary to haul your sorry single-gear cruiser up the Haight Street hill..."
The Wiggle is an extremely flat zig-zag route between Market Street and Golden Gate Park (and westward).
The Wiggle even has its own jingle and PSA.
In 2012 war is happening over the Wiggle.
The route Westward
Take Market outbound.
Right on Duboce Street bikeway. There's a big bike mural here behind the Safeway.
Right on Steiner.
Left on Waller.
Right on Pierce.
Left on Haight.
Right on Scott.
Left on Fell.
You'll be on the Panhandle Path now. It's easy riding westward from here!
Once you reach Steiner there will be signs and green arrows on the street directing you along the Wiggle! So just figure out how to get to the beginning of the route, pay attention, and you'll be fine. It's sooo easy but also so great.
The route Eastward
West-bound wiggle directions can simply be reversed, with the exception of Fell St., which is a one way going west; use Oak instead.
The intersection of Scott and Haight can be subtly annoying in traffic, so it's worth routing around when going eastward.
Since the purpose of the wiggle is to even out/avoid the steep incline getting into the upper haight, on the way back you can just as well sail down Haight St — check your brakes, or your fixie skid marks or what ever.