Don't lube the trigger, its nylon 66 plastic that is self lubricating. If the trigger is too stiff you can try the famous "25 cent trigger job" and you will notice some difference - there are no miracles here but it did make my 26 trigger a little smoother.
http://www.youtube.com/watch?v=OE8ZFj7qll4
Of course you can buy a lighter trigger. Personally i like my trigger pull how it is, stock, and heavy. I'm not going to change the trigger unless it breaks. I have had a negligent discharge long ago, on a 45 auto i bought from a buddy, that had its parts butchered by the previous owner who simply had to have a hair trigger. (No one was hurt and not much was damaged except a wall and my pride, but naturally i never want to have a ND again.)
Plastic to plastic or metal to plastic, as in the lower receiver, clean but it don't lubricate it. It only attracts grit which will wear the plastic faster then leaving it clean and dry.
that said, i do lubricate metal to metal, the parts in the slide, and the parts glock tells me to lube. (I work with machinery and metal to metal moving parts almost always calls for some kind of lubricant.) I lightly lube the extractor, trigger safety and extractor spring and follower with automotive moly grease. The firing pin i clean the hole and the pin, and leave that dry, because again it is metal on plastic (the insert in the hole is plastic).
I could be wrong but that's what everything i've ever learned about machines, tells me to do.
If someone has a good reason not to do this, i'm interested in hearing it.