Grout
Most grout stains are surface stains. Try sandpaper or a Magic Eraser-type sponge to remove them. (Even a pencil eraser works well.)
If you still have stains, try a grout cleaner or a mix of bleach and water. Make sure you're in a well-ventilated area and wear gloves to protect your skin.
Bathtubs
Vinegar is a great cleaning agent for baths. Using a spray bottle, spray vinegar all over the tub. Leave for 15 minutes, then wipe down the tub and rinse.
For stubborn stains, try a mix of lemon juice, baking soda, and vinegar. Work the paste over the stains with a sponge and rinse.
Sinks
Mix 1 cup baking soda with 1/2 cup Borax. Sprinkle in the sink and scrub with a sponge. The mixture is a natural and mild abrasive that will lift any stains.
Wood Cabinets
To clean and rejuvenate wood cabinets, try a solution of equal parts vinegar and water. Use a sponge to remove grease and buildup. (Avoid using steel wool or scrub brushes since they can damage the cabinets' finish.) A paste of water and baking soda can be applied to remove any stubborn stains.
To restore shine, try a mix of 1/4 cup olive oil and 1 cup vinegar. Using a spray bottle, spray your cabinets with the solution and buff with a soft cloth.
Source: http://tinyurl.com/9dxdj2d