Drop the AA usually, but the frame rates have to drop pretty darn far. --- He who stumbles around in darkness with a stick is blind. But he who... sticks out in darkness... is... fluorescent! - Brother Silence
When framerates drop, it's usually a CPU bottleneck because I have a Radeon HD 7950. I lower settings like Shadows and View Distance until I get the framerate I want. Resolution is never lowered except in Terraria where 1080p is too zoomed-out for my tastes.