Scrub away heavy rust build-up with steel wool, then, using WD-40 or turpentine as a lubricant, scour what’s left with 240-grit wet/dry sandpaper.
Soak rusty tools in white vinegar overnight (or longer), then use a scouring pad or crumpled up aluminum foil to rub off the rust, now weakened by the awesome acidic power of vinegar. Use a toothbrush to get at hard-to-reach spots on the tools.
Soak tools in a mixture of water and oxalic powder (you can find it online or at home improvement stores). Oxalic acid is a more powerful rust-buster than vinegar—you may only need to soak the tools for 20 minutes—but it sure isn’t anything you want to get in your eyes or on your skin. Wear goggles and rubber gloves.
Wire wheel + electric drill
For the toughest of rust, coat your tools with kerosene or another lubricant, and tackle them with a drill-powered wire wheel. Finish the job with sandpaper. Rust, you are busted.