One point to note.. when cleaning the slide after a field strip, many people like to place it in a downward position while scrubbing the "bolt face," where the firing pin is. This helps prevent any tiny brass shavings or carbon slipping into the firing pin mechanism by gravity.
There's also a small hole on the bottom of the slide, try not to get any schmutz in there either.
Read your manual about lube for the Glock, doesn't take much and just put it in the right places. You don't have to oil it down like most other weapons. Some good YouTube videos about it as well. Personally I like Gun Butter.