Beat up your furniture. Use your originality to create the nicks, dents, cuts and scrapes that naturally accumulate on wooden furniture over time. For example, whip your vanity with a chain, smack it with a hammer or scratch it with some old keys. Pay special attention to the flat-top surface, corners and edges, which are the likeliest places for natural wear to occur.
Rough up the vanity with a power sander. Your sanding doesn't have to be precise; imprecision, in fact, is the key to giving it a worn look. Sand off any lacquer and most of the paint, and while you're at it, go over a few areas with a rough-grit sandpaper by pressing hard with the power sander. This wears down not only the paint, but the wood itself.
Paint the furniture. Again, you need not be exact in your painting, especially because you are going to paint over it once it dries. Don't worry about the nooks and crannies.
After the furniture dries, paint it again with a contrasting color. For example, if you painted blue before, paint white this time.
Buff away the paint with steel wool to expose the different layers. This gives your vanity the appearance of having been painted, repainted and worn down over the years.
Dip a clean rag in dark wood stain and rub the stain onto the edges and corners of your vanity. Wipe it off immediately; this gives it just enough stain to create the illusion of age and wear.
Seal your vanity with lacquer or varnish to ensure that it doesn't accumulate any actual wear and tear. This preserves your shabby chic look without risking any further damage.