You'll do ok if you simply break your gun down for cleaning and notice where the wear ocurrs. On a 1911, for example, you'll find that the front of the barrel (be generous here), and the top of the barrel hood have wear marks caused by friction. Oil those. Lube the Link, also, and anywhere else you notice wear, such as the locking lugs. Not as much friction happening on the rails as you might think, although that might vary from gun to gun.
For a Sig Pistol, for another example, you might notice that there isn't much wear on the rails, but you'll doubtless see that lube is needed on the barrel, and the top of the barrel hood (you can lube the inside of the top of the frame near the ejection port), and a touch on the inside of the frame where the recoiling slide rubs against the sides of the chamber portion of the barrel. Also, the lock up portion of the barrel (on the bottom) under the chamber. TIP: cotton swabs.
The aforementioned should cover you for cycling reliability. For internal parts, some of which are related to smooth trigger pull, there are marks cause by friction, also. But you won't see them without disassembly. On my SIG Pistols, I use Miltech all along the HAMMER PIVOT pin, and some squirted internally, such as where the sear rubs against the hammer. I also put some Miltech on the safety plunger where it rubs up and down in the frame. Many shooters don't know to do that for a better trigger pull. I use a little lube on both sides of the end of the trigger bar where it attaches to the trigger. I don't use too much, anlywhere,since even Miltech can attract gunk. Overlubing the gun won't hurt it's function, initially, but will attract the above mentioned gunk, dirt, etc. before too long. Finally, on the SIG, I use a good grease on the main spring. Guess what--that can help the trigger pull. Periodically, I clean it all out with Gunscrubber, and start all over.
Lastly, if you completely disassemble the gun, use a slightly oily rag to wipe off the parts and protect them, even if no wear is present. And of course wipe off the frame and slide where you can reach. Leave the firing pin tunnel alone on a 1911. The techs at Sig like a LITTLE lube in there AFTER you squirt it out real good with Gunscrubber thru the firing pin hole at the breach. The reason is that you don't have access to it unless you completely disassemble the slide, (SIG recommends slide disassembly after every 5000 rds for a good cleaning of the firing pin and extractor on their external extractor guns, which are the non stainless variety). I suspect that other guns benefit as well from the above teatment, although Glocks need very little lube. I still lube the barrel, and it's important to use a good grease where the connector rubs against the trigger bar. Hope I wasn't too long winded, and I have little quarrel with those who use different methods to keep their pistols running.