Light oil or grease on the frame: lemon Pledge or similar furniture polish. (Don't get it on rim or disk braking surfaces.)
Heavier, dirtier grease: Simple Green followed by soap & water.
Chain: remove, degunk with a light application of kerosene and scrubbing, reinstall, apply fresh lube.
Caked-on gunk: disassemble, scrape off accumulation, rinse in solvent., re-lube while reassembling.