you can go to secondary when fermentation has completely finished. before that and you could end up stalling fermentation...and if you don't deal with a stuck fermentation properly and bottle anyways, you get bottle bombs.
or just give it 3 weeks in the primary and bottle/keg (at least for most beers)
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10