Step one -
Count exactly how many knobs you'll need. Remember to count every cabinet, closet, drawer and door.
Step two -
Decide what size knobs/handles you want. Don t forget, if you are just replacing existing handles, and you are not too confident with DIY, it may be easier to find handles that fit the existing holes. Obviously if it is a handle with just one screw hole, you will not have much of a problem, just needing to find a similar or larger screw to fit the hole. However if the handle requires two screws, you will need to measure the distance between the centre of both holes, and match that to handles with the same width between their screw holes.
Step three -
Remove the existing handles utilizing the appropriate tool to remove the screws. (For stubborn screws, squirt a little W-D40 onto the screw head.)
Step four -
If you are going for a totally different size handle, you will need to fill the hole that the original handle has left. Use some wood filler, and with your finger, push some filler directly into the hole, and wipe of any surrounding excess.
Once the filler is dry, gently sand back just the filler until it is smooth and flush. Most wood fillers will work fine with stain, so you can now put a matching stain over the filler to disguise it, or paint it if the item is painted.
Step five -
Determine what size screws you need. Knobs generally ship with a 1 ½ – 2" screw, and you should check to be sure this will work for your installation. Doors and drawers will sometimes need two different screw lengths and different pieces of furniture may need different sizes. In addition to length, you must have screws that are the correct diameter. This won't be an issue if you can use the screws that came with your knobs. But if the screws that came with your knob aren't the right length, the best thing to do is figure out the length you need and take the knob to the hardware store with you so that you're sure to get a screw that is the correct diameter.
Step six -
Install the new knobs. Drill holes if needed. The holes you drill should be the correct diameter, and should be drilled perpendicular to the surface. If you drill at an angle it can be hard to get the knobs to screw in tightly.
Using the appropriate tool (flathead or Phillips screwdriver or Allen wrench), turn the screw through the hole and into the hole of the new handle. Tighten the screws after all screws for that handle have been installed and you are satisfied with the fit, the look, and the alignment of the new handle.