If you have a steel frame, use frame-saver on the inside to prevent water damage/rust.
If you have a titanium frame, use anti-seize grease on every single piece of metal that touches the frame (even water bottle cage bolts, cable stops, etc.). Titanium is known to seize with other metals over time.

-Use grease with every bolt/thread/seatpost/etc.
-Cut cable housing with proper tools. Cutting it properly with cause a lot less friction(especially at the cable housing ends), thus extending the life and usability of the cables. Grind the ends of the housing flat.
-Good idea to face and chase bb cups and headtube, even if it is a good manufacturer.