Here's a site with full disassembly, and diagrams showing the "Shepard's Hook" trigger assembly retaining wire:
http://www.ak-47.net/ak47/comp/comp.html
Here's an ever better site:
http://www.gunsnet.net/linx310/fcgremoval.htm
NOTE: this is for the Rumanian rifles, and on these rifles, the hook is remove FORWARD. MOST rifles have to be removed to the REAR.
This wire varies somewhat, but basically, it's a wire "hook" on the LEFT side of the receiver that wraps around the trigger pin, then goes forward and UNDER the hammer pin.
The pins have grooves which the wire interlocks with holding the pins in the receiver.
IN GENERAL (it varies) you use a punch or screwdriver to push the forward "leg" of the wire DOWN from the HAMMER pin, then slide the hammer pin out.
(Note: the pins have a groove the wire locks into. The groove tends to get hung up on the thin receiver, and unless you get it aligned properly, the pin will not come out.
DO NOT hammer or try to drive the pins out, you'll RUIN the receiver. They AREN'T "stuck" the groove is catching on the receiver sides).
After pressing the wire down and getting the hammer pin out, push BACK on the FRONT leg of the pin to get it to unsnap from the trigger pin, then remove it from the receiver.
Depending on the version of the wire, you may be able to push the wire back and remove it before the hammer pin is removed.