I second all the advice above, and I'll add one thing new. If you're willing to take the chances involved with bidding sites like PriceLine (e.g., you aren't set on a specific hotel or room configuration), start looking there 2 weeks before your trip and up to 2 days before your trip. When occupancy rates are low, SF hotels put their extra inventory on there at lower prices. If you do find a last minute bargain there you can cancel the refundable rate stay you booked well in advance. You do have booked a stay already, right?