The only lubrication point on the receiver is under the 'hook' of the connector. This is the most critical point to lubricate for keeping the trigger pull smooth. We recommend a white grease to be applied every few hundred rounds or so to avoid the gritty trigger pull. We at GlockParts.com LLC carry the Mil-Comm TW25B Lubricant Protectant for this application.
The slide has two lubrication points, the rails and the hood of the slide. Just apply a drop on each rail, with the muzzel pointed downward and let gravity allow the drops to run down to the front of the slide.
The 'hood' of the slide. Apply one or two drops of oil just to the left of the screw for the front sight and spread it to the left, towards the ejection port.
Then a couple of drops of oil on the barrel and smooth it out.
Last a drop of oil on each lug of the barrel.
Just remember not to get any oil inside the firing pin channel. This sometimes happens when the slide is over lubricated and oil seeps in around the firing pin safety or the debris hole next to the stripper rail. Notice both in the picture below.