Ok here I'm going to bestow a bit of advice I saw on a Ducati forum but it will apply to any old bike. And it has special relevance if you want to get cheap performance by increasing the compression on your bike, but more of that later.
The ignition system on your bike is built to give a good spark. It's built with enough power that it can give a decent spark over a range of conditions, and can cope with some ageing of the components, especially the spark plug, and still do the business.
But this bike I'm building is 30 years old. That's 30 years of corrosion and deterioration of the components in the ignition system. It starts and runs, so there's no major faults, but it doesn't start too well, and it runs rough.
This might be a familiar story to you - you have a bike, it runs OK, maybe a bit hard starting and rough, but who cares, it starts right? But then it develops a miss-fire, or becomes a complete shit to start. So the first thing you do is check the spark plugs, and they look like crap, so you splash out on some new ones. Job done! it runs great! But not for too long, soon the rough running, and then the miss-fire comes back. So you take the plugs out and clean them. And that cures it again. But it keeps happening...
This is because the ignition system is struggling to cope with all the degradation of the electrical system. With a new spark plug it's OK, just about doing the job. But it's not a real strong spark, so carbon can easily build up on the plug tip, and soon there's a mis-fire.

The HT leads are often a major culprit, and they are (usually) easy to change. But there's way more to it than that - there's degradation of the ignition performance at every step:-
The alternator and reg/rec connections are often corroded, and the wires ageing, so the alternator's not putting out full voltage. The battery and starter motor connections are corroded, the starter cables are undersized, and the battery is weak, so starting reduces battery voltage excessively, which means the charging system spends all your journey trying to recharge the battery, which reduces power available to the ignition system. Then, when you trace the route the power to the coils takes you find it takes a torturous journey around the bike, with a number of points of resistance to pass through - the key switch, the kill switch, and half a dozen connectors, all 30 years old.
Coils are voltage multipliers, the more voltage you put in, the more comes out. So ideally there's the full voltage from a strong alternator going in, but what you've got is a lot less. The chap on the Ducati forum had checked the voltage drop through his bikes electrical system and found that although the alternator was putting out 13.9 volts, only around 9 volts were going into the coils. So by going through the electrical system and cleaning it up, and maybe if necessary using a couple of relays to cut out any problem spots like the kill switch and key switch, you can increase the spark power dramatically.
Of course if you've got an Italian bike it'll be in a worse state after 15 years than a Jap bike will be after 30, if it hasn't already caught fire due to the state of the electrical system.

Then there's another factor that can increase your spark power - the spark gap. The bigger the gap, the more powerful the spark, up to the point that the ignition system can't cope and you start to get a mis-fire. So to get maximum ignition power you need to play around with the plug gap to get the optimum setting. Service manuals give a specified setting, but of course this is very conservative to give a working spark even with a weak ignition system. So this should be considered an absolute minimum. Iridium spark plugs allow for a bigger gap and so a stronger spark too, but again the maximum useable gap will need to be dialed in.

Add all this together and you can get a super strong spark that will cope with big increases in compression, give easy starting and smooth running, without having to spend more than a few quid on a couple of iridium spark plugs, some new leads and maybe a relay or two. Sweet!