Select a wood stain for the job. The light color of oak doesn't make it hard to find a stain that will darken the wood, but you may want to ask a stain sales representative to show you some color samples before you purchase the stain.
Prepare your work area by laying a tarp on your counters, floor, and table. Open a window and all the vents in the room for safety purposes. Remove everything from inside the cabinets.
Remove your drawers and cabinet doors. Lay them flat onto a tarp. Set all hinges and screws aside where they will not interfere with the staining process. Remove any handles, doorstops, and locks.
Sand the face of the drawers, the doors, and the cabinets, moving with the grain. Start with 60 grit sandpaper and work your way up to 140 grit (using 80 grit and 120 grit in between). When you finish, you should no longer see any more of the old stain or blemishes in the wood.
Dust the wood after you finish sanding. Use tack cloth to pick away any remaining sawdust and splinters from the wood.
Wet the surface of the oak with a moist cloth to check for scratches. Oak is such a light wood that you may not see scratches caused by sanding at first. The light layer of moisture will temporarily darken the face of the wood, allowing you to clearly see the lighter scratches caused by the sanding (which you will have to sand out once the wood dries).
Wear gloves to protect your hands from the stain. Wear a smock to protect your clothing. Do not touch anything aside from the wood while your gloves have stain on them.
Dip a paintbrush into the stain. Hold it at an angle over the opening to let any excess stain drip off. Oak is a light-colored wood, so any drips will definitely stand out, even if you stain over them, so preventing a drip is extremely important.
Test the color of the stain by applying a small dab on the hidden underside of a cabinet. The light color of oak might make your stain color a little more vibrant than expected, so it is always wise to test the color before you apply a large amount of it.
Brush the stain onto the wood surface. Use slow, steady strokes. Do not let the strokes of the brush overlap, or you will create a striped effect.
Let the stain dry for five minutes, then rub down the wood surface with a sturdy, dry cloth. This collects the excess stain and allows the first layer of stain to dry faster.
Apply a second layer of stain after the first layer dries. Apply it in the same slow, steady fashion you did the first. It may take a third coat to darken your oak cabinets sufficiently.