To make new brass knobs and trim look antique (if they are not lacquered) with salt and vinegar. Add two tablespoons of salt to a cup of vinegar. Rub the mixture onto the metal, let it set overnight, rinse, and dry. This can be repeated to look older and older each time.
Wood furniture, boxes, etc., can be given an antique patina overnight. Simply wrap them in a trashbag, put an open bowl or jar of ammonia into the bag, and tie it up tightly. The ammonia fumes speed up the natural darkening process of the wood. Be very careful when opening the bag so you don't get a face full of fumes, and don't do this in the house. Check the color every 8 hours or so to see if it is dark enough. If not, tie it back up. Some pieces may require several days. When you see the appropriate color beginning, stop the process -- the wood will darken a little more after it is removed from the bag.
Furniture may have only a small section that needs to be darkened. This could be due to damage that required sanding or a bleach spill. The small area can be darkened with ammonia directly, applied with a small brush. Several applications may be needed because the ammonia evaporates when not in the closed bag. If the process is going too slowly, plastic wrap can be put over the ammonia to prevent evaporation.
Some, not all, furniture in lighter wood types may not have enough tannin to turn dark from the ammonia. These would include birch, maple, pine, and poplar. Tea contains tannin, and strong brewed tea can be applied with a brush. Wait 24 hours before deciding if the color is right or if another coat is needed.