There are many ways to remove rust stains from metal that will get the job accomplished. It largely depends on the item you are working on and how bad the rust stain is. You will need some of the same tools no matter which substance or treatment you will use.
Step One: Natural Removers
There are a few natural remedies for rust stains that require things you may have around the house that may work on your rusted metal. Try making a paste of baking soda and water and using it like a scouring creme with the fine steel wool to remove the rust. Put it on the rust, let it sit for a while (but not until dry), then scour off. If the rust is light, rinsing with water may be sufficient. If you have heavy rust you may need to apply this paste more than once to remove the rust.
Another natural remover is white vinegar used full strength. Pour some on the rusted area, or if the item is small, soak it in a plastic container filled with vinegar until the rust soaks loose. You can use the steel wool or sandpaper to remove the rest of the rust.
If you want to use a lot of muscle, try sanding the rust off if it isn't heavy or deep. It will require some work, but it may be worth it if you don't like the fumes of cleaners.
Step Two: Mineral Spirits
Mineral spirits are very commonly used to remove rust from metal objects, especially tools such as saws. You will want to use this chemical outside due to the fumes. Do not use near fire or flame since it is very flammable. Wear rubber gloves, as it will irritate your skin. If possible, remove the handle if it's a tool because the mineral spirits can take off wood stain and varnish. Pour some mineral spirits in an old can or dish and dip the steel wool into it. Wring out slightly and start rubbing the rusted area. As the rust loosens, use more mineral spirits to remove the excess in a wash sort of fashion. Wipe dry with an old rag that can be disposed of or paper towels. You may need to repeat this process a few times to get all of the rust off. Be sure to dispose of the rags you use in an airtight container to keep them from igniting.
Step Three: Grinder or Sander
If the metal item is very large or the rust is deep, using a shop grinder or sander may be the best solution. This would include rust on a vehicle or large tool or tank. Be sure to remove any flammable liquids if you are working on a tank. Wear goggles and heavy work gloves. Use metal grit grade sanding paper or grinder wheels to scour the rust away. You may expect sparking as you do this if you are unaccustomed to using this type of tool.
Step Four: Prevention
The best way to remove rust is to not get it in the first place. Coat all your hand tools and saws with a very light application of sewing machine oil at least once a year after cleaning them. This will prevent rust.