For me it was this one:
A tip I learned here, and one of the most wonderful timesavers EVAR. Shoot your nails, say when installing baseboard or window trim, through a piece of masking tape. Then apply the filler. Then remove tape. Minimal sanding. I now do a few face-frames that way too... forget about bicuits and pocketscrews... (Only applies when painting afterwards, of course.)
I wish I could remember who posted that tip...but thank you!
r