Have a read of this, all you need is a cheap multimeter.
Is it misfiring all the time? does it run the same with that particular suspect coil disconnected? ie. running on 3 pots all the time, coil connected or disconnected?
Have a look at swapping the suspect lead over first, I'm not sure if they just pull out from the coil or unscrew, if you can get hold of a meter, you can check the resistance of these as well, they all should read the same.
Also check the plug cap and plug it's self, a cracked plug will misfire, has it a screw on nipple on the top of the plug, is it tight? Does the cap fit tightly? Is the lead fitted to the coil and cap tightly?
Try looking at things with a bit of logic, discount the easy things one by one, then try and test and narrow down the others.
So swapping the leads only may move the misfire, it's the lead, swapping the coils may move the misfire, it's a coil. If no matter what you swap and the misfire stays, your problem is else where.