Compression is checked with a compression tester/gauge. You can buy them or major auto parts chains may have them as part of “loaner” tool sets.
You need 4 things to make the thing fire - gas, air, compression, spark. For a single cylinder misfire, put air at the bottom of the list. Lots of people spend a lot of time and money chasing spark and fuel. Its often good to just rule out a compression problem before chasing those things.
If the compression is ok, you need to worry not only about the spark plugs but also the wires & coil/coil pack/distributor (whatever the set up is). Then you also need to worry about the injectors. You can swap the #2 injector with another one to see if the misfire moves with the injector. On the fuel end, you have to keep in mind that a misfire can come from either too little fuel or too much.
A repair manual for the car will help you in sorting these things out.