The deadline for consideration for a Screen Actors Guild Award nomination is October 27. Actors may submit themselves or give permission to producers, studios and agents et al to submit on their behalf. Nominees will be selected by two separate film and television panels, each made up of 2,100 SAG members (randomly selected). Ballots are then mailed on November 23, with voting closing on December 12 and nominees announced on December 14. The SAG Awards take place on January 29.
Last year's SAG winners included eventual Oscar-winners Colin Firth (The King's Speech), Natalie Portman (Black Swan), Christian Bale (The Fighter), Melissa Leo (The Fighter) and best picture Oscar-winner The Kings Speech (Outstanding Performance by a Cast).
Here's the complete rules and regulations.