Patterns. Pattern everything. Patterns in patterns. Patterns in patterns in patterns. Patterns of holes, patterns of everything. Favorite trick, favorite tool in Creo. One of the underclassmen asked me how I could CAD a drive train in 20 minutes: patterns.
Also center-rectangles and thin wall extrusions are great.
Generally, the newest thing I find that saves me time is my new favorite trick.
(I understand that these things might be old hat to a lot of people but we're all at various points in our educations
)
In my personal opinion patterns are one of the most powerful model/geometry creation tools in Creo-- learning how (and when) to use them and the limitations is probably a small book of knowledge.