Chevrolet Repair: spark plug stuck, aluminum head, thread insert

Question
how do I get a sparkplug out for replacement when it is stuck I can turn it a half turn but it wont come out Didn't put antiseize on last time i changed them. only 1 wont come out

Answer
Spray a bunch of Liquid Wrench, or some other penetrating fluid around the base of the plug. Wiggle it a little with the socket.

More penetrant...possibly blow it in with compressed air.

Didn't happen to mention what engine.
If it has aluminum head, you may end up twisting out the threads.
They are not terribly hard to repair with a "Helicoil" thread insert kit. Drills the hole out, and replaces the threads with stainless steel threads of the same size.

Van