When it comes to M1911 reliability, the big two things you need to keep in mind are the extractor and the barrel ramp. I'll go over both. People are correct in that the older M1911s were hella reliable because of their looser clearances (read: NOT tolerances). To be more specific though, back then, the extractor wasn't so damn tight. Today, manufacturers are building weapons with CNC machinery which means ridiculously precise parts construction. This is great for super tight builds and getting the maximum amount of accuracy out of the gun. Not so much for reliability on an M1911. The best way to test your extractor is to field strip it, then take the slide and, from the bottom, insert a .45 ACP cartridge where the bullet would usually begin to feed into the barrel. If it's hard to press in, it's too tight. This is an easy fix though. Just take it down to a gunsmith and have them loosen it, buy another extractor (maybe something from Wilson Combat), or simply just shoot it until the extractor finally starts loosening up.
After that, the second thing is the barrel ramp. Now, extractor tightness aside, if you're using a stock standard military issue government model 5" M1911A1, and you're using standard .45 ACP ball ammo, you shouldn't have any issues at all. If you're using more exotic ammo though like hollow points, then the feed ramp very quickly is going to start coming into play. On that aforementioned standard issue military M1911A1, the feed ramp is a combination of the ramp within the frame and the small ramp leading out of the barrel. For exotic ammo, this is a problem. Again though, the fix is easy, although this time, a little spendy. You will need to get another barrel that has the full feed ramp attached directly to the barrel instead of the ramp being a combination of the frame and the barrel.
If you're still having issues, make sure that the magazine you're using is a good one. Make sure that the spring is strong enough to continually and reliably feed ammo into the weapon. This is not really an issue with the pistol itself though. It's a much more general problem any gun can have, but it is still often overlooked, so just keep that in mind.
So, M1911 reliability aside, make sure when you get an M1911 that the guide rod is the "GI" style guide rod and not an extended or full-length one. An extended guide rod doesn't offer anything and will, in fact, complicate the field stripping process of the M1911, making you need a tool to do so. With a standard GI guide rod, you can field strip and put the pistol back together entirely by hand.
And with that, there is one more thing that you'll probably find really cool. The M1911 can actually chamber much hotter rounds such as the .45 Super and the .460 Rowland (about equal to a .44 magnum in power) due to it's ridiculously sturdy all-steel construction and its large size. This will require a barrel and spring change. There are conversion kits available for this. For the .460 Rowland, you'll also probably need a barrel with a compensator. Now, I have heard of people running +P+ and .45 Super ammo through their unmodified M1911A1 without an issue or maybe just a spring change, but I generally wouldn't do this as you'll have much more of a possibility of slide and frame cracking or an improper ammunition discharge (gun blows up due to the higher powered cartridge being more unsupported at the bottom) along with it just generally causing excessive wear and tear on your handgun even if it technically seems to work fine.