First you need to choose the piece of furniture you wish to paint, then you need to prepare it to be painted. This means removing all the metal bits; hinges and handles. With the metal removed, you're ready to get rid of the paint or varnish currently on the piece – wallpaper is recommended, but a paint or varnish remover should also do the trick. Once the piece has been sanded, you'll need to wipe it down with warm water to get rid of the dust sanding inevitably leaves behind.
The next step depends on the condition of the piece. If it's in poor condition then primer is recommended, if it's in good condition then an extra coat of paint should suffice – make sure it dries before you apply the second coat, and keep each layer even. When painting, make sure to brush in the direction of the wood grain, and do not go too crazy with the paint, good shabby chic does not have much paint on it – so keep your brush with minimal paint on it.
After leaving it for at least 24 hours it's time to distress the piece – if you're not a fan of the distracted look, then just add some varnish or wax to the piece to protect the paint and the wood, and you're all done. For an authentic look you'll need to pick out the areas which would normally be a little more worn than the rest. These areas are usually around the edges of the piece, around the drawers, handles, and any raised edges – different pieces are likely to have different areas which would be more worn.
The wallpaper is needed again now; sand the areas you've identified as points of wear and tear in one direction until you've got the desired look. Although this can be a little unpredictable, if you want to brave the piece you can beat it, preferably using a metal object; do not get too carried away with this asitting it too hard could cause quite a bit more damage than you intended. Start off with gentle taps and work your way up until you get the amount of bruising that you wanted. When you're done with that, finish the piece off by adding a little varnish to protect the wood, but not too much as this can detract from the shabby chic look.
Tip – if you want the wood grain to show through the paint after sanding, it's a good idea to use materials such as pine; painted pine furniture looks great.