Re: Instructions/diagrams for a 24 tab switch
For general testing of connections, you can pick up a cheap multimeter for as little as $10.
You should get one with a continuity test option (it beeps whenever a connection is made between the 2 probes). They usually have different modes (e.g. for measuring resistance, current etc) and are accurate to varying degrees depending on price. A $10 multimeter is fine for most things, unless you need super-accurate figures on resistances etc.
You can then verify the lugs you expect to be hot are hot by using the probes on continuity test mode, which can save a lot of swearing if you accidentally wire something back to front! (been there, done that!)