Lubrication points are somewhat a matter of personal preference.
Personally I lube:
The "tail" of the bolt where it slides into the hole in the bolt carrier.
The locking lugs on the bolt. (Grease)
The rails of the bolt, and where they ride in the receiver.
The front face of the hammer. (Grease)
The contact points of the hammer "ears" that slide under the trigger. (Grease)
The front "hook" area of the disconnecter. (Grease)
The "stem" area of the bolt carrier behind the gas piston.
The recoil spring and guide.
Grease works well since it doesn't dry out or evaporate, wash away, run off, sling off, or wick away. It stay put and lubricates.