You need a sparkplug socket wrench to remove a plug. Don't try it with an ordinary wrench, its not worth the damage you will do to the plug and the engine.
Also to tighten a used plug its more like 1/4 of a turn after finger tight, since the crush washer is already crushed and it just needs to be resnugged. Do not overtighten a plug. The soft aluminum head will strip before the hard steel sparkplug thread, and you will be into a nasty and needless repair effort if you strip the plug threads.
2004 Rebel 250, 2003 BMW K1200GT (roadburner), 2004 BMW R1200GS(all purpose),
1973 Norton Interstate (in a box in the basement)
1968 Triumph Bonneville